rework Stateful::set_state() patch to avoid default version argument

git-svn-id: svn://localhost/ardour2/branches/3.0@5787 d708f5d6-7413-0410-9779-e7cbd77b26cf

90 files changed, 205 insertions, 186 deletions

diff --git a/libs/ardour/amp.cc b/libs/ardour/amp.cc
index bf3e7cee68..2100d736a8 100644
--- a/libs/ardour/amp.cc
+++ b/libs/ardour/amp.cc
@@ -339,7 +339,7 @@ Amp::set_state (const XMLNode& node, int version)
 {
 	const XMLProperty* prop;
 
-	Processor::set_state (node);
+	Processor::set_state (node, version);
 	prop = node.property ("gain");
 
 	if (prop) {
diff --git a/libs/ardour/ardour/amp.h b/libs/ardour/ardour/amp.h
index 3cd1bf13dd..724b1095a1 100644
--- a/libs/ardour/ardour/amp.h
+++ b/libs/ardour/ardour/amp.h
@@ -55,7 +55,7 @@ public:
 	void apply_gain_automation(bool yn) { _apply_gain_automation = yn; }
 
 	XMLNode& state (bool full);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	static void apply_gain (BufferSet& bufs, nframes_t nframes, gain_t initial, gain_t target);
 	static void apply_simple_gain(BufferSet& bufs, nframes_t nframes, gain_t target);
diff --git a/libs/ardour/ardour/audio_diskstream.h b/libs/ardour/ardour/audio_diskstream.h
index 507b148d82..ae2176cbab 100644
--- a/libs/ardour/ardour/audio_diskstream.h
+++ b/libs/ardour/ardour/audio_diskstream.h
@@ -126,7 +126,7 @@ class AudioDiskstream : public Diskstream
 	/* stateful */
 
 	XMLNode& get_state(void);
-	int      set_state(const XMLNode& node, int version = 3000);
+	int      set_state(const XMLNode& node, int version);
 
 	void monitor_input (bool);
 
diff --git a/libs/ardour/ardour/audio_track.h b/libs/ardour/ardour/audio_track.h
index 585d1a1e72..fc5b4255b3 100644
--- a/libs/ardour/ardour/audio_track.h
+++ b/libs/ardour/ardour/audio_track.h
@@ -55,7 +55,7 @@ class AudioTrack : public Track
 	boost::shared_ptr<Region> bounce (InterThreadInfo&);
 	boost::shared_ptr<Region> bounce_range (nframes_t start, nframes_t end, InterThreadInfo&, bool enable_processing);
 
-	int set_state(const XMLNode&, int version = 3000);
+	int set_state(const XMLNode&, int version);
 
   protected:
 	XMLNode& state (bool full);
diff --git a/libs/ardour/ardour/audiofilesource.h b/libs/ardour/ardour/audiofilesource.h
index 6b93ced905..95c7db4385 100644
--- a/libs/ardour/ardour/audiofilesource.h
+++ b/libs/ardour/ardour/audiofilesource.h
@@ -72,7 +72,7 @@ public:
 	int setup_peakfile ();
 
 	XMLNode& get_state ();
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	bool can_truncate_peaks() const { return !destructive(); }
 	bool can_be_analysed() const    { return _length > 0; }
diff --git a/libs/ardour/ardour/audioplaylist.h b/libs/ardour/ardour/audioplaylist.h
index 25595def8c..277fe5a8e1 100644
--- a/libs/ardour/ardour/audioplaylist.h
+++ b/libs/ardour/ardour/audioplaylist.h
@@ -50,7 +50,7 @@ class AudioPlaylist : public ARDOUR::Playlist
 
         nframes_t read (Sample *dst, Sample *mixdown, float *gain_buffer, nframes_t start, nframes_t cnt, uint32_t chan_n=0);
 
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	sigc::signal<void,boost::shared_ptr<Crossfade> > NewCrossfade;
 
diff --git a/libs/ardour/ardour/audioregion.h b/libs/ardour/ardour/audioregion.h
index 5e9031c897..a8055575f9 100644
--- a/libs/ardour/ardour/audioregion.h
+++ b/libs/ardour/ardour/audioregion.h
@@ -107,7 +107,7 @@ class AudioRegion : public Region
 	virtual nframes_t read_raw_internal (Sample*, sframes_t, nframes_t, int channel) const;
 
 	XMLNode& state (bool);
-	int      set_state (const XMLNode&, int version = 3000);
+	int      set_state (const XMLNode&, int version);
 
 	static void set_default_fade (float steepness, nframes_t len);
 	bool fade_in_is_default () const;
@@ -219,7 +219,7 @@ class AudioRegion : public Region
 
 	AudioRegion (Session& s, nframes_t, nframes_t, std::string name);
 
-	int set_live_state (const XMLNode&, Change&, bool send);
+	int set_live_state (const XMLNode&, int version, Change&, bool send);
 };
 
 } /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/audiosource.h b/libs/ardour/ardour/audiosource.h
index eebd1dd5d9..dd6076630d 100644
--- a/libs/ardour/ardour/audiosource.h
+++ b/libs/ardour/ardour/audiosource.h
@@ -79,7 +79,7 @@ class AudioSource : virtual public Source,
 	mutable sigc::signal<void,nframes_t,nframes_t>  PeakRangeReady;
 
 	XMLNode& get_state ();
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	int rename_peakfile (Glib::ustring newpath);
 	void touch_peakfile ();
diff --git a/libs/ardour/ardour/automation_list.h b/libs/ardour/ardour/automation_list.h
index 5f074385a3..69c8e38c95 100644
--- a/libs/ardour/ardour/automation_list.h
+++ b/libs/ardour/ardour/automation_list.h
@@ -80,7 +80,7 @@ class AutomationList : public PBD::StatefulDestructible, public Evoral::ControlL
 	bool touching() const { return _touching; }
 
 	XMLNode& get_state (); 
-	int set_state (const XMLNode &, int version = 3000);
+	int set_state (const XMLNode &, int version);
 	XMLNode& state (bool full);
 	XMLNode& serialize_events ();
 
diff --git a/libs/ardour/ardour/control_protocol_manager.h b/libs/ardour/ardour/control_protocol_manager.h
index d1f059dc62..d2b1796b18 100644
--- a/libs/ardour/ardour/control_protocol_manager.h
+++ b/libs/ardour/ardour/control_protocol_manager.h
@@ -70,7 +70,7 @@ struct ControlProtocolInfo {
 
 	void set_protocol_states (const XMLNode&);
 
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 	XMLNode& get_state (void);
 
   private:
diff --git a/libs/ardour/ardour/crossfade.h b/libs/ardour/ardour/crossfade.h
index 8a7773c035..5d8e0235fb 100644
--- a/libs/ardour/ardour/crossfade.h
+++ b/libs/ardour/ardour/crossfade.h
@@ -75,7 +75,7 @@ class Crossfade : public ARDOUR::AudioRegion
 	bool operator== (const ARDOUR::Crossfade&);
 
 	XMLNode& get_state (void);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	boost::shared_ptr<ARDOUR::AudioRegion> in() const { return _in; }
 	boost::shared_ptr<ARDOUR::AudioRegion> out() const { return _out; }
diff --git a/libs/ardour/ardour/delivery.h b/libs/ardour/ardour/delivery.h
index ef78c9bd45..beccab73ae 100644
--- a/libs/ardour/ardour/delivery.h
+++ b/libs/ardour/ardour/delivery.h
@@ -89,7 +89,7 @@ public:
 	static sigc::signal<void,nframes_t> CycleStart;
 
 	XMLNode& state (bool full);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	/* Panning */
 
diff --git a/libs/ardour/ardour/diskstream.h b/libs/ardour/ardour/diskstream.h
index 5427dc644d..23ba6a713e 100644
--- a/libs/ardour/ardour/diskstream.h
+++ b/libs/ardour/ardour/diskstream.h
@@ -130,7 +130,7 @@ class Diskstream : public SessionObject, public boost::noncopyable
 
 	/* Stateful */
 	virtual XMLNode& get_state(void) = 0;
-	virtual int      set_state(const XMLNode&, int version = 3000) = 0;
+	virtual int      set_state(const XMLNode&, int version) = 0;
 	
 	virtual void monitor_input (bool) {}
 
diff --git a/libs/ardour/ardour/file_source.h b/libs/ardour/ardour/file_source.h
index 5a9c2a9c56..ce34f1c0d4 100644
--- a/libs/ardour/ardour/file_source.h
+++ b/libs/ardour/ardour/file_source.h
@@ -46,7 +46,7 @@ public:
 	bool                 is_embedded () const { return _is_embedded; }
 	uint16_t             channel()      const { return _channel; }
 
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	int set_source_name (const Glib::ustring& newname, bool destructive);
 
diff --git a/libs/ardour/ardour/internal_return.h b/libs/ardour/ardour/internal_return.h
index e896200c93..dfd37a4de5 100644
--- a/libs/ardour/ardour/internal_return.h
+++ b/libs/ardour/ardour/internal_return.h
@@ -38,7 +38,7 @@ class InternalReturn : public Return
 
 	XMLNode& state(bool full);
 	XMLNode& get_state(void);
-	int set_state(const XMLNode&, int version = 3000);
+	int set_state(const XMLNode&, int version);
 
 	void run (BufferSet& bufs, sframes_t start_frame, sframes_t end_frame, nframes_t nframes);
 	bool configure_io (ChanCount in, ChanCount out);
diff --git a/libs/ardour/ardour/internal_send.h b/libs/ardour/ardour/internal_send.h
index d62be9eafa..3b069af194 100644
--- a/libs/ardour/ardour/internal_send.h
+++ b/libs/ardour/ardour/internal_send.h
@@ -38,7 +38,7 @@ class InternalSend : public Send
 
 	XMLNode& state(bool full);
 	XMLNode& get_state(void);
-	int set_state(const XMLNode& node, int version = 3000);
+	int set_state(const XMLNode& node, int version);
 	
 	void run (BufferSet& bufs, sframes_t start_frame, sframes_t end_frame, nframes_t nframes);
 	bool feeds (boost::shared_ptr<Route> other) const;
diff --git a/libs/ardour/ardour/io.h b/libs/ardour/ardour/io.h
index 9a13ced942..5d64fae580 100644
--- a/libs/ardour/ardour/io.h
+++ b/libs/ardour/ardour/io.h
@@ -137,7 +137,7 @@ class IO : public SessionObject, public Latent
 
 	virtual XMLNode& state (bool full);
 	XMLNode& get_state (void);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 	int set_state_2X (const XMLNode&, int, bool);
 
 	static int  disable_connecting (void);
diff --git a/libs/ardour/ardour/io_processor.h b/libs/ardour/ardour/io_processor.h
index fdb0429bca..0d564bb00c 100644
--- a/libs/ardour/ardour/io_processor.h
+++ b/libs/ardour/ardour/io_processor.h
@@ -72,7 +72,7 @@ class IOProcessor : public Processor
 	sigc::signal<void,IOProcessor*,uint32_t> AutomationChanged;
 
 	XMLNode& state (bool full_state);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 	
   protected:
 	boost::shared_ptr<IO> _input;
diff --git a/libs/ardour/ardour/ladspa_plugin.h b/libs/ardour/ardour/ladspa_plugin.h
index b08f3e5afa..656c13afae 100644
--- a/libs/ardour/ardour/ladspa_plugin.h
+++ b/libs/ardour/ardour/ladspa_plugin.h
@@ -99,7 +99,7 @@ class LadspaPlugin : public ARDOUR::Plugin
 	bool parameter_is_toggled(uint32_t) const;
 
 	XMLNode& get_state();
-	int      set_state (const XMLNode&, int version = 3000);
+	int      set_state (const XMLNode&, int version);
 	bool     save_preset(std::string name);
 
 	bool has_editor() const { return false; }
@@ -133,7 +133,7 @@ class LadspaPlugin : public ARDOUR::Plugin
 	void init (void *mod, uint32_t index, nframes_t rate);
 	void run_in_place (nframes_t nsamples);
 	void latency_compute_run ();
-	int set_state_2X (const XMLNode&, int version = 3000);
+	int set_state_2X (const XMLNode&, int version);
 };
 
 class LadspaPluginInfo : public PluginInfo {
diff --git a/libs/ardour/ardour/location.h b/libs/ardour/ardour/location.h
index cbc0782a4a..b48db52d92 100644
--- a/libs/ardour/ardour/location.h
+++ b/libs/ardour/ardour/location.h
@@ -71,7 +71,7 @@ class Location : public PBD::StatefulDestructible
 	}
 
 	Location (const Location& other);
-	Location (const XMLNode&, int version = 3000);
+	Location (const XMLNode&);
 	Location* operator= (const Location& other);
 
 	bool locked() const { return _locked; }
@@ -125,7 +125,7 @@ class Location : public PBD::StatefulDestructible
 	XMLNode& cd_info_node (const std::string &, const std::string &);
 
 	XMLNode& get_state (void);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
   private:
 	std::string   _name;
@@ -155,7 +155,7 @@ class Locations : public PBD::StatefulDestructible
 	void clear_ranges ();
 
 	XMLNode& get_state (void);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
         Location *get_location_by_id(PBD::ID);
 
 	Location* auto_loop_location () const;
diff --git a/libs/ardour/ardour/lv2_plugin.h b/libs/ardour/ardour/lv2_plugin.h
index de42512cfe..f2773a3d6c 100644
--- a/libs/ardour/ardour/lv2_plugin.h
+++ b/libs/ardour/ardour/lv2_plugin.h
@@ -115,7 +115,7 @@ class LV2Plugin : public ARDOUR::Plugin
 	static uint32_t midi_event_type() { return _midi_event_type; }
 
 	XMLNode& get_state();
-	int      set_state(const XMLNode& node);
+	int      set_state(const XMLNode& node, int version);
 	bool     save_preset(std::string uri);
 	bool     load_preset(const std::string uri);
 	virtual std::vector<Plugin::PresetRecord> get_presets();
diff --git a/libs/ardour/ardour/midi_diskstream.h b/libs/ardour/ardour/midi_diskstream.h
index aab752d591..e152989229 100644
--- a/libs/ardour/ardour/midi_diskstream.h
+++ b/libs/ardour/ardour/midi_diskstream.h
@@ -75,7 +75,7 @@ class MidiDiskstream : public Diskstream
 
 	/* stateful */
 	XMLNode& get_state(void);
-	int set_state(const XMLNode&, int version = 3000);
+	int set_state(const XMLNode&, int version);
 
 	void monitor_input (bool);
 
diff --git a/libs/ardour/ardour/midi_model.h b/libs/ardour/ardour/midi_model.h
index a5b0e36b26..6c7e26119a 100644
--- a/libs/ardour/ardour/midi_model.h
+++ b/libs/ardour/ardour/midi_model.h
@@ -70,7 +70,7 @@ public:
 		void operator()();
 		void undo();
 		
-		int set_state (const XMLNode&, int version = 3000);
+		int set_state (const XMLNode&, int version);
 		XMLNode& get_state ();
 
 		void add(const boost::shared_ptr< Evoral::Note<TimeType> > note);
@@ -114,7 +114,7 @@ public:
 		void operator()();
 		void undo();
 		
-		int set_state (const XMLNode&, int version = 3000);
+		int set_state (const XMLNode&, int version);
 		XMLNode& get_state ();
 
 		void change (const boost::shared_ptr<Evoral::Note<TimeType> > note,
diff --git a/libs/ardour/ardour/midi_playlist.h b/libs/ardour/ardour/midi_playlist.h
index dc315edb12..c83bf80a28 100644
--- a/libs/ardour/ardour/midi_playlist.h
+++ b/libs/ardour/ardour/midi_playlist.h
@@ -50,7 +50,7 @@ public:
 	nframes_t read (MidiRingBuffer<nframes_t>& buf,
 			nframes_t start, nframes_t cnt, uint32_t chan_n=0);
 
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	bool destroy_region (boost::shared_ptr<Region>);
 
diff --git a/libs/ardour/ardour/midi_region.h b/libs/ardour/ardour/midi_region.h
index ddb3109ff6..c796ee742b 100644
--- a/libs/ardour/ardour/midi_region.h
+++ b/libs/ardour/ardour/midi_region.h
@@ -68,7 +68,7 @@ class MidiRegion : public Region
 			NoteMode  mode = Sustained) const;
 
 	XMLNode& state (bool);
-	int      set_state (const XMLNode&, int version = 3000);
+	int      set_state (const XMLNode&, int version);
 
 	int separate_by_channel (ARDOUR::Session&, std::vector< boost::shared_ptr<Region> >&) const;
 
@@ -118,7 +118,7 @@ class MidiRegion : public Region
 
   protected:
 
-	int set_live_state (const XMLNode&, Change&, bool send);
+	int set_live_state (const XMLNode&, int version, Change&, bool send);
 };
 
 } /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/midi_source.h b/libs/ardour/ardour/midi_source.h
index 8a09aad6c8..bffcde5192 100644
--- a/libs/ardour/ardour/midi_source.h
+++ b/libs/ardour/ardour/midi_source.h
@@ -91,7 +91,7 @@ class MidiSource : virtual public Source
 	mutable sigc::signal<void,sframes_t,nframes_t> ViewDataRangeReady;
 
 	XMLNode& get_state ();
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	bool length_mutable() const { return true; }
 
diff --git a/libs/ardour/ardour/midi_track.h b/libs/ardour/ardour/midi_track.h
index 9f19c6590c..c273395a74 100644
--- a/libs/ardour/ardour/midi_track.h
+++ b/libs/ardour/ardour/midi_track.h
@@ -59,7 +59,7 @@ public:
 	boost::shared_ptr<Region>  bounce_range (
 			nframes_t start, nframes_t end, InterThreadInfo&, bool enable_processing);
 
-	int set_state(const XMLNode&, int version = 3000);
+	int set_state(const XMLNode&, int version);
 
 	void midi_panic(void);
 	bool write_immediate_event(size_t size, const uint8_t* buf);
diff --git a/libs/ardour/ardour/mute_master.h b/libs/ardour/ardour/mute_master.h
index 39ad9ffd61..70015f3a35 100644
--- a/libs/ardour/ardour/mute_master.h
+++ b/libs/ardour/ardour/mute_master.h
@@ -65,7 +65,7 @@ class MuteMaster : public AutomationControl
 	sigc::signal<void> MutePointChanged;
 
 	XMLNode& get_state();
-	int set_state(const XMLNode&, int version = 3000);
+	int set_state(const XMLNode&, int version);
 
   private:
 	AutomationList* _automation;
diff --git a/libs/ardour/ardour/named_selection.h b/libs/ardour/ardour/named_selection.h
index 4911dd8c50..d41f104e1a 100644
--- a/libs/ardour/ardour/named_selection.h
+++ b/libs/ardour/ardour/named_selection.h
@@ -44,7 +44,7 @@ struct NamedSelection : public PBD::Stateful
 
     XMLNode& get_state (void);
 
-    int set_state (const XMLNode&, int version = 3000);
+    int set_state (const XMLNode&, int version);
 
     static sigc::signal<void,NamedSelection*> NamedSelectionCreated;
 };
diff --git a/libs/ardour/ardour/panner.h b/libs/ardour/ardour/panner.h
index 6a435ec235..86cd486113 100644
--- a/libs/ardour/ardour/panner.h
+++ b/libs/ardour/ardour/panner.h
@@ -73,7 +73,7 @@ class StreamPanner : public sigc::trackable, public PBD::Stateful
 	sigc::signal<void> Changed;      /* for position */
 	sigc::signal<void> StateChanged; /* for mute */
 
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 	virtual XMLNode& state (bool full_state) = 0;
 
 	Panner & get_parent() { return parent; }
@@ -150,7 +150,7 @@ class EqualPowerStereoPanner : public BaseStereoPanner
 
 	XMLNode& state (bool full_state); 
 	XMLNode& get_state (void); 
-	int      set_state (const XMLNode&, int version = 3000);
+	int      set_state (const XMLNode&, int version);
 
   private:
 	void update ();
@@ -171,7 +171,7 @@ class Multi2dPanner : public StreamPanner
 
 	XMLNode& state (bool full_state);
 	XMLNode& get_state (void);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	/* old school automation loading */
 
@@ -228,7 +228,7 @@ public:
 
 	XMLNode& get_state (void);
 	XMLNode& state (bool full);
-	int      set_state (const XMLNode&, int version = 3000);
+	int      set_state (const XMLNode&, int version);
 
 	static bool equivalent (pan_t a, pan_t b) {
 		return fabsf (a - b) < 0.002; // about 1 degree of arc for a stereo panner
diff --git a/libs/ardour/ardour/playlist.h b/libs/ardour/ardour/playlist.h
index 01bb12db8d..aa661b8588 100644
--- a/libs/ardour/ardour/playlist.h
+++ b/libs/ardour/ardour/playlist.h
@@ -124,7 +124,7 @@ class Playlist : public SessionObject,
 	void foreach_region (sigc::slot<void, boost::shared_ptr<Region> >);
 
 	XMLNode& get_state ();
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 	XMLNode& get_template ();
 
 	sigc::signal<void,bool> InUse;
diff --git a/libs/ardour/ardour/plugin_insert.h b/libs/ardour/ardour/plugin_insert.h
index 82111a5a4d..ea8228f5fc 100644
--- a/libs/ardour/ardour/plugin_insert.h
+++ b/libs/ardour/ardour/plugin_insert.h
@@ -45,14 +45,14 @@ class PluginInsert : public Processor
 {
   public:
 	PluginInsert (Session&, boost::shared_ptr<Plugin>);
-	PluginInsert (Session&, const XMLNode&, int version = 3000);
+	PluginInsert (Session&, const XMLNode&);
 	~PluginInsert ();
 
 	static const std::string port_automation_node_name;
 
 	XMLNode& state(bool);
 	XMLNode& get_state(void);
-	int set_state(const XMLNode&, int version = 3000);
+	int set_state(const XMLNode&, int version);
 
 	void run (BufferSet& in, sframes_t start_frame, sframes_t end_frame, nframes_t nframes);
 	void silence (nframes_t nframes);
diff --git a/libs/ardour/ardour/port_insert.h b/libs/ardour/ardour/port_insert.h
index 73dacf7d68..3283415e6d 100644
--- a/libs/ardour/ardour/port_insert.h
+++ b/libs/ardour/ardour/port_insert.h
@@ -44,12 +44,12 @@ class PortInsert : public IOProcessor
 {
   public:
 	PortInsert (Session&, boost::shared_ptr<MuteMaster> mm);
-	PortInsert (Session&, boost::shared_ptr<MuteMaster> mm, const XMLNode&, int version = 3000);
+	PortInsert (Session&, boost::shared_ptr<MuteMaster> mm, const XMLNode&);
 	~PortInsert ();
 
 	XMLNode& state(bool full);
 	XMLNode& get_state(void);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	void run (BufferSet& bufs, sframes_t start_frame, sframes_t end_frame, nframes_t nframes);
 
diff --git a/libs/ardour/ardour/processor.h b/libs/ardour/ardour/processor.h
index 1e78777edd..473bb97130 100644
--- a/libs/ardour/ardour/processor.h
+++ b/libs/ardour/ardour/processor.h
@@ -91,7 +91,7 @@ class Processor : public SessionObject, public AutomatableControls, public Laten
 
 	virtual XMLNode& state (bool full);
 	XMLNode& get_state (void);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 	
 	void *get_gui () const { return _gui; }
 	void  set_gui (void *p) { _gui = p; }
diff --git a/libs/ardour/ardour/rc_configuration.h b/libs/ardour/ardour/rc_configuration.h
index d0dc042bb1..555c925a01 100644
--- a/libs/ardour/ardour/rc_configuration.h
+++ b/libs/ardour/ardour/rc_configuration.h
@@ -37,7 +37,7 @@ class RCConfiguration : public Configuration
 	RCConfiguration();
 
 	void map_parameters (sigc::slot<void, std::string>);
-	int set_state (XMLNode const &, int version = 3000);
+	int set_state (XMLNode const &, int version);
 	XMLNode& get_state ();
 	XMLNode& get_variables ();
 	void set_variables (XMLNode const &);
diff --git a/libs/ardour/ardour/region.h b/libs/ardour/ardour/region.h
index d341489249..0f1f10eff8 100644
--- a/libs/ardour/ardour/region.h
+++ b/libs/ardour/ardour/region.h
@@ -241,8 +241,8 @@ class Region
 
 	XMLNode&         get_state ();
 	virtual XMLNode& state (bool);
-	virtual int      set_state (const XMLNode&, int version = 3000);
-	virtual int      set_live_state (const XMLNode&, Change&, bool send);
+	virtual int      set_state (const XMLNode&, int version);
+	virtual int      set_live_state (const XMLNode&, int version, Change&, bool send);
 
 	virtual boost::shared_ptr<Region> get_parent() const;
 
diff --git a/libs/ardour/ardour/return.h b/libs/ardour/ardour/return.h
index 3232e93295..b3212fe4a0 100644
--- a/libs/ardour/ardour/return.h
+++ b/libs/ardour/ardour/return.h
@@ -54,7 +54,7 @@ public:
 
 	XMLNode& state(bool full);
 	XMLNode& get_state(void);
-	int      set_state(const XMLNode&, int version = 3000);
+	int      set_state(const XMLNode&, int version);
 
 	uint32_t pans_required() const { return _configured_input.n_audio(); }
 
diff --git a/libs/ardour/ardour/route.h b/libs/ardour/ardour/route.h
index ac3c6f89f3..51e4d99335 100644
--- a/libs/ardour/ardour/route.h
+++ b/libs/ardour/ardour/route.h
@@ -66,9 +66,8 @@ class Route : public SessionObject, public AutomatableControls
 		ControlOut = 0x4
 	};
 
-	Route (Session&, std::string name, Flag flags = Flag(0),
-	       DataType default_type = DataType::AUDIO);
-	Route (Session&, const XMLNode&, int, DataType default_type = DataType::AUDIO);
+	Route (Session&, std::string name, Flag flags = Flag(0), DataType default_type = DataType::AUDIO);
+	Route (Session&, const XMLNode&, DataType default_type = DataType::AUDIO);
 	virtual ~Route();
 
 	boost::shared_ptr<IO> input() const { return _input; }
@@ -251,7 +250,7 @@ class Route : public SessionObject, public AutomatableControls
 	/* stateful */
 
 	XMLNode& get_state();
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 	virtual XMLNode& get_template();
 
 	XMLNode& get_processor_state ();
diff --git a/libs/ardour/ardour/route_group.h b/libs/ardour/ardour/route_group.h
index 124f3c9b3f..0f71093377 100644
--- a/libs/ardour/ardour/route_group.h
+++ b/libs/ardour/ardour/route_group.h
@@ -131,7 +131,7 @@ public:
 
 	XMLNode& get_state ();
 	
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 	
 private:
 	Session& _session;
diff --git a/libs/ardour/ardour/send.h b/libs/ardour/ardour/send.h
index 13b7adbbf2..f9f13ee309 100644
--- a/libs/ardour/ardour/send.h
+++ b/libs/ardour/ardour/send.h
@@ -53,7 +53,7 @@ class Send : public Delivery
 
 	XMLNode& state(bool full);
 	XMLNode& get_state(void);
-	int set_state(const XMLNode&, int version = 3000);
+	int set_state(const XMLNode&, int version);
 
 	uint32_t pans_required() const { return _configured_input.n_audio(); }
 
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index c5b793730c..cc94d3878c 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -468,7 +468,7 @@ class Session : public PBD::StatefulDestructible, public boost::noncopyable
 	static std::vector<std::string*>* possible_states (std::string path);
 
 	XMLNode& get_state();
-	int      set_state(const XMLNode& node, int version = 3000); // not idempotent
+	int      set_state(const XMLNode& node, int version); // not idempotent
 	XMLNode& get_template();
 
 	/// The instant xml file is written to the session directory
@@ -849,7 +849,7 @@ class Session : public PBD::StatefulDestructible, public boost::noncopyable
 	public:
 		GlobalRouteStateCommand (Session&, void*);
 		GlobalRouteStateCommand (Session&, const XMLNode& node);
-		int set_state (const XMLNode&, int version = 3000);
+		int set_state (const XMLNode&, int version);
 		XMLNode& get_state ();
 
 	protected:
@@ -899,7 +899,7 @@ class Session : public PBD::StatefulDestructible, public boost::noncopyable
 		void operator()();
 		void undo();
 		XMLNode &get_state();
-		int set_state (const XMLNode&, int version = 3000);
+		int set_state (const XMLNode&, int version);
 		void mark();
 
 	protected:
@@ -1170,8 +1170,8 @@ class Session : public PBD::StatefulDestructible, public boost::noncopyable
 
 	std::string _current_snapshot_name;
 
-	XMLTree* state_tree;
-	bool     state_was_pending;
+	XMLTree*         state_tree;
+	bool             state_was_pending;
 	StateOfTheState _state_of_the_state;
 
 	void     auto_save();
diff --git a/libs/ardour/ardour/session_configuration.h b/libs/ardour/ardour/session_configuration.h
index 20e14f37d5..20df86ca4d 100644
--- a/libs/ardour/ardour/session_configuration.h
+++ b/libs/ardour/ardour/session_configuration.h
@@ -30,7 +30,7 @@ public:
 	SessionConfiguration ();
 
 	void map_parameters (sigc::slot<void, std::string>);
-	int set_state (XMLNode const &, int version = 3000);
+	int set_state (XMLNode const &, int version);
 	XMLNode& get_state ();
 	XMLNode& get_variables ();
 	void set_variables (XMLNode const &);
diff --git a/libs/ardour/ardour/session_metadata.h b/libs/ardour/ardour/session_metadata.h
index 7813788e55..481e21c338 100644
--- a/libs/ardour/ardour/session_metadata.h
+++ b/libs/ardour/ardour/session_metadata.h
@@ -107,7 +107,7 @@ class SessionMetadata : public PBD::StatefulDestructible
 
 	/*** Serialization ***/
 	XMLNode & get_state ();
-	int set_state (const XMLNode &, int version = 3000);
+	int set_state (const XMLNode &, int version);
 
   private:
 
diff --git a/libs/ardour/ardour/smf_source.h b/libs/ardour/ardour/smf_source.h
index 3c6364532a..fbaa049d8a 100644
--- a/libs/ardour/ardour/smf_source.h
+++ b/libs/ardour/ardour/smf_source.h
@@ -58,7 +58,7 @@ public:
 	void mark_streaming_write_completed ();
 
 	XMLNode& get_state ();
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	void load_model (bool lock=true, bool force_reload=false);
 	void destroy_model ();
diff --git a/libs/ardour/ardour/source.h b/libs/ardour/ardour/source.h
index c34c5a9158..1ffca509fd 100644
--- a/libs/ardour/ardour/source.h
+++ b/libs/ardour/ardour/source.h
@@ -76,7 +76,7 @@ class Source : public SessionObject, public boost::noncopyable
 	virtual void session_saved() {}
 
 	XMLNode& get_state ();
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 	
 	bool         destructive() const       { return (_flags & Destructive); }
 	bool         writable () const         { return (_flags & Writable); }
diff --git a/libs/ardour/ardour/tempo.h b/libs/ardour/ardour/tempo.h
index 742919c77a..658330cf82 100644
--- a/libs/ardour/ardour/tempo.h
+++ b/libs/ardour/ardour/tempo.h
@@ -212,7 +212,7 @@ class TempoMap : public PBD::StatefulDestructible
 	void set_length (nframes_t frames);
 
 	XMLNode& get_state (void);
-	int set_state (const XMLNode&, int version = 3000);
+	int set_state (const XMLNode&, int version);
 
 	void dump (std::ostream&) const;
 	void clear ();
diff --git a/libs/ardour/ardour/track.h b/libs/ardour/ardour/track.h
index 74cbe399df..02cab70a84 100644
--- a/libs/ardour/ardour/track.h
+++ b/libs/ardour/ardour/track.h
@@ -82,7 +82,7 @@ class Track : public Route
 
 	XMLNode&    get_state();
 	XMLNode&    get_template();
-	virtual int set_state (const XMLNode&, int version = 3000) = 0;
+	virtual int set_state (const XMLNode&, int version) = 0;
 	static void zero_diskstream_id_in_xml (XMLNode&);
 
 	boost::shared_ptr<PBD::Controllable> rec_enable_control() { return _rec_enable_control; }
@@ -96,7 +96,7 @@ class Track : public Route
 	sigc::signal<void> FreezeChange;
 
   protected:
-	Track (Session& sess, const XMLNode& node, int, DataType default_type = DataType::AUDIO);
+	Track (Session& sess, const XMLNode& node, DataType default_type = DataType::AUDIO);
 
 	virtual XMLNode& state (bool full) = 0;
 
diff --git a/libs/ardour/ardour/user_bundle.h b/libs/ardour/ardour/user_bundle.h
index f590ec1ebe..c124e2e722 100644
--- a/libs/ardour/ardour/user_bundle.h
+++ b/libs/ardour/ardour/user_bundle.h
@@ -38,7 +38,7 @@ class UserBundle : public Bundle, public PBD::Stateful {
 	XMLNode& get_state ();
 
   private:
-	int set_state (XMLNode const &, int version = 3000);
+	int set_state (XMLNode const &, int version);
 };
 
 }
diff --git a/libs/ardour/audio_diskstream.cc b/libs/ardour/audio_diskstream.cc
index bb0b715f3b..e43cbd7891 100644
--- a/libs/ardour/audio_diskstream.cc
+++ b/libs/ardour/audio_diskstream.cc
@@ -90,7 +90,7 @@ AudioDiskstream::AudioDiskstream (Session& sess, const XMLNode& node)
 	in_set_state = true;
 	init (Recordable);
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		in_set_state = false;
 		throw failed_constructor();
 	}
diff --git a/libs/ardour/audio_playlist.cc b/libs/ardour/audio_playlist.cc
index 812aa8783b..eb4913e727 100644
--- a/libs/ardour/audio_playlist.cc
+++ b/libs/ardour/audio_playlist.cc
@@ -46,7 +46,7 @@ AudioPlaylist::AudioPlaylist (Session& session, const XMLNode& node, bool hidden
 	assert(!prop || DataType(prop->value()) == DataType::AUDIO);
 
 	in_set_state++;
-	set_state (node);
+	set_state (node, Stateful::loading_state_version);
 	in_set_state--;
 }
 
@@ -566,7 +566,7 @@ AudioPlaylist::set_state (const XMLNode& node, int version)
 
 	in_set_state++;
 
-	Playlist::set_state (node);
+	Playlist::set_state (node, version);
 
 	freeze ();
 
diff --git a/libs/ardour/audio_track.cc b/libs/ardour/audio_track.cc
index 600cad6aa2..c1862fb5b0 100644
--- a/libs/ardour/audio_track.cc
+++ b/libs/ardour/audio_track.cc
@@ -57,9 +57,9 @@ AudioTrack::AudioTrack (Session& sess, string name, Route::Flag flag, TrackMode
 }
 
 AudioTrack::AudioTrack (Session& sess, const XMLNode& node, int version)
-	: Track (sess, node, version)
+	: Track (sess, node)
 {
-	_set_state (node, version, false);
+	_set_state (node, Stateful::loading_state_version, false);
 }
 
 AudioTrack::~AudioTrack ()
@@ -300,7 +300,7 @@ AudioTrack::_set_state (const XMLNode& node, int version, bool call_base)
 		child = *niter;
 
 		if (child->name() == X_("recenable")) {
-			_rec_enable_control->set_state (*child);
+			_rec_enable_control->set_state (*child, version);
 			_session.add_controllable (_rec_enable_control);
 		}
 	}
@@ -809,7 +809,7 @@ AudioTrack::unfreeze ()
 			for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
 				for (vector<FreezeRecordProcessorInfo*>::iterator ii = _freeze_record.processor_info.begin(); ii != _freeze_record.processor_info.end(); ++ii) {
 					if ((*ii)->id == (*i)->id()) {
-						(*i)->set_state (((*ii)->state));
+						(*i)->set_state (((*ii)->state), Stateful::current_state_version);
 						break;
 					}
 				}
diff --git a/libs/ardour/audiofilesource.cc b/libs/ardour/audiofilesource.cc
index 5430d300fb..8de786eb0e 100644
--- a/libs/ardour/audiofilesource.cc
+++ b/libs/ardour/audiofilesource.cc
@@ -121,7 +121,7 @@ AudioFileSource::AudioFileSource (Session& s, const XMLNode& node, bool must_exi
 	, AudioSource (s, node)
 	, FileSource (s, node, must_exist)
 {
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor ();
 	}
 
@@ -260,15 +260,15 @@ AudioFileSource::get_state ()
 int
 AudioFileSource::set_state (const XMLNode& node, int version)
 {
-	if (Source::set_state (node)) {
+	if (Source::set_state (node, version)) {
 		return -1;
 	}
 
-	if (AudioSource::set_state (node)) {
+	if (AudioSource::set_state (node, version)) {
 		return -1;
 	}
 
-	if (FileSource::set_state (node)) {
+	if (FileSource::set_state (node, version)) {
 		return -1;
 	}
 
diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index 47dfc6c902..a5c52ce671 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -236,7 +236,7 @@ AudioRegion::AudioRegion (boost::shared_ptr<AudioSource> src, const XMLNode& nod
 
 	init ();
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 
@@ -255,7 +255,7 @@ AudioRegion::AudioRegion (SourceList& srcs, const XMLNode& node)
 {
 	init ();
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 
@@ -634,13 +634,13 @@ AudioRegion::state (bool full)
 }
 
 int
-AudioRegion::set_live_state (const XMLNode& node, Change& what_changed, bool send)
+AudioRegion::set_live_state (const XMLNode& node, int version, Change& what_changed, bool send)
 {
 	const XMLNodeList& nlist = node.children();
 	const XMLProperty *prop;
 	LocaleGuard lg (X_("POSIX"));
 
-	Region::set_live_state (node, what_changed, false);
+	Region::set_live_state (node, version, what_changed, false);
 
 	uint32_t old_flags = _flags;
 
@@ -691,7 +691,7 @@ AudioRegion::set_live_state (const XMLNode& node, Change& what_changed, bool sen
 
 			_envelope->clear ();
 
-			if ((prop = child->property ("default")) != 0 || _envelope->set_state (*child)) {
+			if ((prop = child->property ("default")) != 0 || _envelope->set_state (*child, version)) {
 				set_default_envelope ();
 			}
 
@@ -707,7 +707,7 @@ AudioRegion::set_live_state (const XMLNode& node, Change& what_changed, bool sen
 			} else {
 				XMLNode* grandchild = child->child ("AutomationList");
 				if (grandchild) {
-					_fade_in->set_state (*grandchild);
+					_fade_in->set_state (*grandchild, version);
 				}
 			}
 
@@ -728,7 +728,7 @@ AudioRegion::set_live_state (const XMLNode& node, Change& what_changed, bool sen
 			} else {
 				XMLNode* grandchild = child->child ("AutomationList");
 				if (grandchild) {
-					_fade_out->set_state (*grandchild);
+					_fade_out->set_state (*grandchild, version);
 				}
 			}
 
@@ -758,7 +758,7 @@ AudioRegion::set_state (const XMLNode& node, int version)
 	   to handle the relevant stuff.
 	*/
 
-	return Region::set_state (node);
+	return Region::set_state (node, version);
 }
 
 void
diff --git a/libs/ardour/audiosource.cc b/libs/ardour/audiosource.cc
index d50ad0c6b7..93e201b8c2 100644
--- a/libs/ardour/audiosource.cc
+++ b/libs/ardour/audiosource.cc
@@ -85,7 +85,7 @@ AudioSource::AudioSource (Session& s, const XMLNode& node)
 	peak_leftover_size = 0;
 	peak_leftovers = 0;
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 }
diff --git a/libs/ardour/automation_list.cc b/libs/ardour/automation_list.cc
index be3c38f29b..c0a652275c 100644
--- a/libs/ardour/automation_list.cc
+++ b/libs/ardour/automation_list.cc
@@ -100,7 +100,7 @@ AutomationList::AutomationList (const XMLNode& node, Evoral::Parameter id)
 	_state = Off;
 	_style = Absolute;
 
-	set_state (node);
+	set_state (node, Stateful::loading_state_version);
 
 	if (id) {
 		_parameter = id;
@@ -368,7 +368,7 @@ AutomationList::set_state (const XMLNode& node, int version)
 
 		if ((nsos = node.child (X_("AutomationList")))) {
 			/* new school in old school clothing */
-			return set_state (*nsos);
+			return set_state (*nsos, version);
 		}
 
 		/* old school */
diff --git a/libs/ardour/control_protocol_manager.cc b/libs/ardour/control_protocol_manager.cc
index 8546a41e66..0e687988d2 100644
--- a/libs/ardour/control_protocol_manager.cc
+++ b/libs/ardour/control_protocol_manager.cc
@@ -74,7 +74,7 @@ ControlProtocolManager::set_session (Session& s)
 			(*i)->requested = false;
 
 			if ((*i)->protocol && (*i)->state) {
-				(*i)->protocol->set_state (*(*i)->state);
+				(*i)->protocol->set_state (*(*i)->state, Stateful::loading_state_version);
 			}
 		}
 	}
diff --git a/libs/ardour/crossfade.cc b/libs/ardour/crossfade.cc
index 65ad1e25fb..c69eeea21d 100644
--- a/libs/ardour/crossfade.cc
+++ b/libs/ardour/crossfade.cc
@@ -157,7 +157,7 @@ Crossfade::Crossfade (const Playlist& playlist, XMLNode& node)
 	initialize();
 	_active = true;
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 }
diff --git a/libs/ardour/delivery.cc b/libs/ardour/delivery.cc
index 5f264c5b7e..5b063ad566 100644
--- a/libs/ardour/delivery.cc
+++ b/libs/ardour/delivery.cc
@@ -109,7 +109,7 @@ Delivery::Delivery (Session& s, boost::shared_ptr<MuteMaster> mm, const XMLNode&
 {
 	_panner = boost::shared_ptr<Panner>(new Panner (_name, _session));
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor ();
 	}
 
@@ -136,7 +136,7 @@ Delivery::Delivery (Session& s, boost::shared_ptr<IO> out, boost::shared_ptr<Mut
 {
 	_panner = boost::shared_ptr<Panner>(new Panner (_name, _session));
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor ();
 	}
 
@@ -376,7 +376,7 @@ Delivery::set_state (const XMLNode& node, int version)
 {
 	const XMLProperty* prop;
 
-	if (IOProcessor::set_state (node)) {
+	if (IOProcessor::set_state (node, version)) {
 		return -1;
 	}
 
@@ -390,7 +390,7 @@ Delivery::set_state (const XMLNode& node, int version)
 	XMLNode* pan_node = node.child (X_("Panner"));
 
 	if (pan_node) {
-		_panner->set_state (*pan_node);
+		_panner->set_state (*pan_node, version);
 	}
 
 	reset_panner ();
diff --git a/libs/ardour/globals.cc b/libs/ardour/globals.cc
index acd7da1bc5..d893c1e54b 100644
--- a/libs/ardour/globals.cc
+++ b/libs/ardour/globals.cc
@@ -298,6 +298,12 @@ ARDOUR::init (bool use_vst, bool try_optimization)
 
 	(void) bindtextdomain(PACKAGE, LOCALEDIR);
 
+	/* provide a state version for the few cases that need it and are not
+	   driven by reading state from disk (e.g. undo/redo)
+	*/
+
+	Stateful::current_state_version = CURRENT_SESSION_FILE_VERSION;
+
 	setup_enum_writer ();
 
 	// allow ardour the absolute maximum number of open files
@@ -360,7 +366,7 @@ ARDOUR::init_post_engine ()
 
 	XMLNode* node;
 	if ((node = Config->control_protocol_state()) != 0) {
-		ControlProtocolManager::instance().set_state (*node);
+		ControlProtocolManager::instance().set_state (*node, Stateful::loading_state_version);
 	}
 }
 
diff --git a/libs/ardour/internal_return.cc b/libs/ardour/internal_return.cc
index 9f828ab47b..8a3baf5bda 100644
--- a/libs/ardour/internal_return.cc
+++ b/libs/ardour/internal_return.cc
@@ -133,7 +133,7 @@ InternalReturn::get_state()
 int
 InternalReturn::set_state (const XMLNode& node, int version)
 {
-	return Return::set_state (node);
+	return Return::set_state (node, version);
 }
 
 bool
diff --git a/libs/ardour/internal_send.cc b/libs/ardour/internal_send.cc
index abc6ced05c..d70889a27c 100644
--- a/libs/ardour/internal_send.cc
+++ b/libs/ardour/internal_send.cc
@@ -49,7 +49,7 @@ InternalSend::InternalSend (Session& s, boost::shared_ptr<MuteMaster> mm, boost:
 InternalSend::InternalSend (Session& s, boost::shared_ptr<MuteMaster> mm, const XMLNode& node)
 	: Send (s, mm, node, Delivery::Aux /* will be reset in set_state() */)
 {
-	set_state (node);
+	set_state (node, Stateful::loading_state_version);
 }
 
 InternalSend::~InternalSend ()
@@ -175,7 +175,7 @@ InternalSend::set_state (const XMLNode& node, int version)
 {
 	const XMLProperty* prop;
 
-	Send::set_state (node);
+	Send::set_state (node, version);
 
 	if ((prop = node.property ("target")) != 0) {
 
diff --git a/libs/ardour/io.cc b/libs/ardour/io.cc
index f49692a910..5bb51bfa18 100644
--- a/libs/ardour/io.cc
+++ b/libs/ardour/io.cc
@@ -93,7 +93,7 @@ IO::IO (Session& s, const XMLNode& node, DataType dt)
 	_active = true;
 	pending_state_node = 0;
 
-	set_state (node);
+	set_state (node, Stateful::loading_state_version);
 	setup_bundles ();
 }
 
diff --git a/libs/ardour/io_processor.cc b/libs/ardour/io_processor.cc
index 2f42c724bf..21a2b10313 100644
--- a/libs/ardour/io_processor.cc
+++ b/libs/ardour/io_processor.cc
@@ -152,7 +152,7 @@ IOProcessor::set_state (const XMLNode& node, int version)
 	const XMLProperty *prop;
 	const XMLNode *io_node = 0;
 
-	Processor::set_state(node);
+	Processor::set_state(node, version);
 
 	if ((prop = node.property ("own-input")) != 0) {
 		_own_input = string_is_affirmative (prop->value());
@@ -176,7 +176,7 @@ IOProcessor::set_state (const XMLNode& node, int version)
 		}
 
 		if (io_node) {
-			_input->set_state(*io_node);
+			_input->set_state(*io_node, version);
 
 			// legacy sessions: use IO name
 			if ((prop = node.property ("name")) == 0) {
@@ -198,7 +198,7 @@ IOProcessor::set_state (const XMLNode& node, int version)
 		}
 
 		if (io_node) {
-			_output->set_state(*io_node);
+			_output->set_state(*io_node, version);
 
 			// legacy sessions: use IO name
 			if ((prop = node.property ("name")) == 0) {
diff --git a/libs/ardour/location.cc b/libs/ardour/location.cc
index 5fb0442eba..7b9e706c36 100644
--- a/libs/ardour/location.cc
+++ b/libs/ardour/location.cc
@@ -59,9 +59,9 @@ Location::Location (const Location& other)
 	_locked = false;
 }
 
-Location::Location (const XMLNode& node, int version)
+Location::Location (const XMLNode& node)
 {
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor ();
 	}
 }
diff --git a/libs/ardour/lv2_plugin.cc b/libs/ardour/lv2_plugin.cc
index 0fb766e7d4..38774104af 100644
--- a/libs/ardour/lv2_plugin.cc
+++ b/libs/ardour/lv2_plugin.cc
@@ -354,7 +354,7 @@ LV2Plugin::has_editor() const
 }
 
 int
-LV2Plugin::set_state(const XMLNode& node)
+LV2Plugin::set_state(const XMLNode& node, int version)
 {
 	XMLNodeList nodes;
 	XMLProperty *prop;
diff --git a/libs/ardour/midi_diskstream.cc b/libs/ardour/midi_diskstream.cc
index 4cae900074..a1604858e4 100644
--- a/libs/ardour/midi_diskstream.cc
+++ b/libs/ardour/midi_diskstream.cc
@@ -98,7 +98,7 @@ MidiDiskstream::MidiDiskstream (Session& sess, const XMLNode& node)
 	in_set_state = true;
 	init (Recordable);
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		in_set_state = false;
 		throw failed_constructor();
 	}
diff --git a/libs/ardour/midi_model.cc b/libs/ardour/midi_model.cc
index df34d13a24..eb69a2a906 100644
--- a/libs/ardour/midi_model.cc
+++ b/libs/ardour/midi_model.cc
@@ -112,7 +112,7 @@ MidiModel::DeltaCommand::DeltaCommand(boost::shared_ptr<MidiModel> m, const XMLN
 	: _model(m)
 {
 	assert(_model);
-	set_state(node);
+	set_state(node, Stateful::loading_state_version);
 }
 
 void
@@ -321,7 +321,7 @@ MidiModel::DiffCommand::DiffCommand(boost::shared_ptr<MidiModel> m, const XMLNod
 	: _model(m)
 {
 	assert(_model);
-	set_state(node);
+	set_state(node, Stateful::loading_state_version);
 }
 
 void
diff --git a/libs/ardour/midi_playlist.cc b/libs/ardour/midi_playlist.cc
index b0fd5de24e..8d030b949e 100644
--- a/libs/ardour/midi_playlist.cc
+++ b/libs/ardour/midi_playlist.cc
@@ -48,7 +48,7 @@ MidiPlaylist::MidiPlaylist (Session& session, const XMLNode& node, bool hidden)
 	assert(prop && DataType(prop->value()) == DataType::MIDI);
 
 	in_set_state++;
-	set_state (node);
+	set_state (node, Stateful::loading_state_version);
 	in_set_state--;
 }
 
@@ -192,7 +192,7 @@ MidiPlaylist::set_state (const XMLNode& node, int version)
 	in_set_state++;
 	freeze ();
 
-	Playlist::set_state (node);
+	Playlist::set_state (node, version);
 
 	thaw();
 	in_set_state--;
diff --git a/libs/ardour/midi_region.cc b/libs/ardour/midi_region.cc
index f22a1994bf..3ced46df9f 100644
--- a/libs/ardour/midi_region.cc
+++ b/libs/ardour/midi_region.cc
@@ -91,7 +91,7 @@ MidiRegion::MidiRegion (boost::shared_ptr<const MidiRegion> other)
 MidiRegion::MidiRegion (boost::shared_ptr<MidiSource> src, const XMLNode& node)
 	: Region (src, node)
 {
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 
@@ -103,7 +103,7 @@ MidiRegion::MidiRegion (boost::shared_ptr<MidiSource> src, const XMLNode& node)
 MidiRegion::MidiRegion (const SourceList& srcs, const XMLNode& node)
 	: Region (srcs, node)
 {
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 
@@ -249,12 +249,12 @@ MidiRegion::state (bool full)
 }
 
 int
-MidiRegion::set_live_state (const XMLNode& node, Change& what_changed, bool send)
+MidiRegion::set_live_state (const XMLNode& node, int version, Change& what_changed, bool send)
 {
 	const XMLProperty *prop;
 	LocaleGuard lg (X_("POSIX"));
 
-	Region::set_live_state (node, what_changed, false);
+	Region::set_live_state (node, version, what_changed, false);
 
 	uint32_t old_flags = _flags;
 
@@ -292,7 +292,7 @@ MidiRegion::set_state (const XMLNode& node, int version)
 	   to handle the relevant stuff.
 	*/
 
-	return Region::set_state (node);
+	return Region::set_state (node, version);
 }
 
 void
diff --git a/libs/ardour/midi_source.cc b/libs/ardour/midi_source.cc
index e90e90aa32..53b1d2c9a5 100644
--- a/libs/ardour/midi_source.cc
+++ b/libs/ardour/midi_source.cc
@@ -72,7 +72,7 @@ MidiSource::MidiSource (Session& s, const XMLNode& node)
 	_read_data_count = 0;
 	_write_data_count = 0;
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 }
diff --git a/libs/ardour/midi_track.cc b/libs/ardour/midi_track.cc
index 6f036f803c..68ff7de1e2 100644
--- a/libs/ardour/midi_track.cc
+++ b/libs/ardour/midi_track.cc
@@ -67,7 +67,7 @@ MidiTrack::MidiTrack (Session& sess, string name, Route::Flag flag, TrackMode mo
 }
 
 MidiTrack::MidiTrack (Session& sess, const XMLNode& node, int version)
-	: Track (sess, node, version, DataType::MIDI)
+	: Track (sess, node, DataType::MIDI)
 	, _immediate_events(1024) // FIXME: size?
 	, _step_edit_ring_buffer(64) // FIXME: size?
 	, _note_mode(Sustained)
@@ -75,7 +75,7 @@ MidiTrack::MidiTrack (Session& sess, const XMLNode& node, int version)
 	, _default_channel (0)
 	, _midi_thru (true)
 {
-	_set_state (node, version, false);
+	_set_state (node, Stateful::loading_state_version, false);
 }
 
 MidiTrack::~MidiTrack ()
@@ -232,7 +232,7 @@ MidiTrack::_set_state (const XMLNode& node, int version, bool call_base)
 		child = *niter;
 
 		if (child->name() == X_("recenable")) {
-			_rec_enable_control->set_state (*child);
+			_rec_enable_control->set_state (*child, version);
 			_session.add_controllable (_rec_enable_control);
 		}
 	}
diff --git a/libs/ardour/panner.cc b/libs/ardour/panner.cc
index 993cbe39f8..a867130b51 100644
--- a/libs/ardour/panner.cc
+++ b/libs/ardour/panner.cc
@@ -496,18 +496,18 @@ EqualPowerStereoPanner::set_state (const XMLNode& node, int version)
 		set_position (pos, true);
 	}
 
-	StreamPanner::set_state (node);
+	StreamPanner::set_state (node, version);
 
 	for (XMLNodeConstIterator iter = node.children().begin(); iter != node.children().end(); ++iter) {
 
 		if ((*iter)->name() == X_("Controllable")) {
 			if ((prop = (*iter)->property("name")) != 0 && prop->value() == "panner") {
-				_control->set_state (**iter);
+				_control->set_state (**iter, version);
 			}
 
 		} else if ((*iter)->name() == X_("Automation")) {
 
-			_control->alist()->set_state (*((*iter)->children().front()));
+			_control->alist()->set_state (*((*iter)->children().front()), version);
 
 			if (_control->alist()->automation_state() != Off) {
 				set_position (_control->list()->eval (parent.session().transport_frame()));
@@ -1154,7 +1154,7 @@ Panner::set_state (const XMLNode& node, int version)
 						sp = pan_plugins[i].factory (*this, Evoral::Parameter(PanAutomation, 0, num_panners));
 						num_panners++;
 
-						if (sp->set_state (**niter) == 0) {
+						if (sp->set_state (**niter, version) == 0) {
 							_streampanners.push_back (sp);
 						}
 
diff --git a/libs/ardour/playlist.cc b/libs/ardour/playlist.cc
index aebcb59f3d..a072d4977b 100644
--- a/libs/ardour/playlist.cc
+++ b/libs/ardour/playlist.cc
@@ -1845,7 +1845,7 @@ Playlist::set_state (const XMLNode& node, int version)
 
 				Change what_changed = Change (0);
 
-				if (region->set_live_state (*child, what_changed, true)) {
+				if (region->set_live_state (*child, version, what_changed, true)) {
 					error << _("Playlist: cannot reset region state from XML") << endmsg;
 					continue;
 				}
diff --git a/libs/ardour/plugin_insert.cc b/libs/ardour/plugin_insert.cc
index 14ea464555..2a5ef29a45 100644
--- a/libs/ardour/plugin_insert.cc
+++ b/libs/ardour/plugin_insert.cc
@@ -81,12 +81,12 @@ PluginInsert::PluginInsert (Session& s, boost::shared_ptr<Plugin> plug)
 	ProcessorCreated (this); /* EMIT SIGNAL */
 }
 
-PluginInsert::PluginInsert (Session& s, const XMLNode& node, int version)
+PluginInsert::PluginInsert (Session& s, const XMLNode& node)
 	: Processor (s, "unnamed plugin insert"),
           _signal_analysis_collected_nframes(0),
           _signal_analysis_collect_nframes_max(0)
 {
-	if (set_state (node, version)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 
@@ -836,7 +836,7 @@ PluginInsert::set_state(const XMLNode& node, int version)
 					data().control(Evoral::Parameter(PluginAutomation, 0, port_id), true));
 
 			if (!child->children().empty()) {
-				c->alist()->set_state (*child->children().front());
+				c->alist()->set_state (*child->children().front(), version);
 			} else {
 				if ((cprop = child->property("auto")) != 0) {
 
diff --git a/libs/ardour/port_insert.cc b/libs/ardour/port_insert.cc
index 04a145aa52..3b02bf41da 100644
--- a/libs/ardour/port_insert.cc
+++ b/libs/ardour/port_insert.cc
@@ -48,12 +48,12 @@ PortInsert::PortInsert (Session& s, boost::shared_ptr<MuteMaster> mm)
 	ProcessorCreated (this); /* EMIT SIGNAL */
 }
 
-PortInsert::PortInsert (Session& s, boost::shared_ptr<MuteMaster> mm, const XMLNode& node, int version)
+PortInsert::PortInsert (Session& s, boost::shared_ptr<MuteMaster> mm, const XMLNode& node)
 	: IOProcessor (s, true, true, "unnamed port insert")
 	, _out (new Delivery (s, _output, mm, _name, Delivery::Insert))
 
 {
-	if (set_state (node, version)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 
@@ -138,7 +138,7 @@ PortInsert::set_state (const XMLNode& node, int version)
 		}
 	}
 
-	Processor::set_state (*insert_node);
+	Processor::set_state (*insert_node, version);
 
 	return 0;
 }
diff --git a/libs/ardour/processor.cc b/libs/ardour/processor.cc
index e1db982fe1..a52db49224 100644
--- a/libs/ardour/processor.cc
+++ b/libs/ardour/processor.cc
@@ -82,7 +82,7 @@ Processor::Processor (Session& session, const XMLNode& node)
 	, _configured(false)
 	, _gui(0)
 {
-	set_state (node);
+	set_state (node, Stateful::loading_state_version);
 	_pending_active = _active;
 }
 
diff --git a/libs/ardour/rc_configuration.cc b/libs/ardour/rc_configuration.cc
index afa9a2a4c3..725225b8d0 100644
--- a/libs/ardour/rc_configuration.cc
+++ b/libs/ardour/rc_configuration.cc
@@ -97,7 +97,7 @@ RCConfiguration::load_state ()
 				return -1;
 			}
 
-			if (set_state (*tree.root())) {
+			if (set_state (*tree.root(), Stateful::current_state_version)) {
 				error << string_compose(_("Ardour: system configuration file \"%1\" not loaded successfully."), rcfile) << endmsg;
 				return -1;
 			}
@@ -132,7 +132,7 @@ RCConfiguration::load_state ()
 				return -1;
 			}
 
-			if (set_state (*tree.root())) {
+			if (set_state (*tree.root(), Stateful::current_state_version)) {
 				error << string_compose(_("Ardour: user configuration file \"%1\" not loaded successfully."), rcfile) << endmsg;
 				return -1;
 			}
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index 244312bc0a..903452ca03 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -298,7 +298,7 @@ Region::Region (const SourceList& srcs, const XMLNode& node)
 {
 	use_sources (srcs);
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 
@@ -328,7 +328,7 @@ Region::Region (boost::shared_ptr<Source> src, const XMLNode& node)
 {
 	_sources.push_back (src);
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 
@@ -1172,7 +1172,7 @@ Region::get_state ()
 }
 
 int
-Region::set_live_state (const XMLNode& node, Change& what_changed, bool send)
+Region::set_live_state (const XMLNode& node, int version, Change& what_changed, bool send)
 {
 	const XMLNodeList& nlist = node.children();
 	const XMLProperty *prop;
@@ -1355,7 +1355,7 @@ Region::set_state (const XMLNode& node, int version)
 
 	_first_edit = EditChangesNothing;
 
-	set_live_state (node, what_changed, true);
+	set_live_state (node, version, what_changed, true);
 
 	return 0;
 }
diff --git a/libs/ardour/return.cc b/libs/ardour/return.cc
index 69aa2f700e..f5122f3a5f 100644
--- a/libs/ardour/return.cc
+++ b/libs/ardour/return.cc
@@ -58,7 +58,7 @@ Return::Return (Session& s, const XMLNode& node, bool internal)
 	_amp.reset (new Amp (_session, boost::shared_ptr<MuteMaster>()));
 	_meter.reset (new PeakMeter (_session));
 
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 
@@ -114,7 +114,7 @@ Return::set_state (const XMLNode& node, int version)
 		}
 	}
 
-	IOProcessor::set_state (*insert_node);
+	IOProcessor::set_state (*insert_node, version);
 
 	return 0;
 }
diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index 7e453653dc..5621f08049 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -96,7 +96,7 @@ Route::Route (Session& sess, string name, Flag flg, DataType default_type)
 	_meter_connection = Metering::connect (mem_fun (*this, &Route::meter));
 }
 
-Route::Route (Session& sess, const XMLNode& node, int version, DataType default_type)
+Route::Route (Session& sess, const XMLNode& node, DataType default_type)
 	: SessionObject (sess, "toBeReset")
 	, AutomatableControls (sess)
 	, _solo_control (new SoloControllable (X_("solo"), *this))
@@ -105,7 +105,7 @@ Route::Route (Session& sess, const XMLNode& node, int version, DataType default_
 {
 	init ();
 
-	_set_state (node, version, false);
+	_set_state (node, Stateful::loading_state_version, false);
 
 	/* now that we have _meter, its safe to connect to this */
 
@@ -748,7 +748,7 @@ Route::add_processor_from_xml (const XMLNode& node, ProcessorList::iterator iter
 			} else if (prop->value() == "meter") {
 
 				if (_meter) {
-					if (_meter->set_state (node)) {
+					if (_meter->set_state (node, Stateful::loading_state_version)) {
 						return false;
 					} else {
 						return true;
@@ -763,7 +763,7 @@ Route::add_processor_from_xml (const XMLNode& node, ProcessorList::iterator iter
 				/* amp always exists */
 
 				processor = _amp;
-				if (processor->set_state (node)) {
+				if (processor->set_state (node, Stateful::loading_state_version)) {
 					return false;
 				} else {
 					/* never any reason to add it */
@@ -777,7 +777,7 @@ Route::add_processor_from_xml (const XMLNode& node, ProcessorList::iterator iter
 			} else if (prop->value() == "intreturn") {
 
 				if (_intreturn) {
-					if (_intreturn->set_state (node)) {
+					if (_intreturn->set_state (node, Stateful::loading_state_version)) {
 						return false;
 					} else {
 						return true;
@@ -789,7 +789,7 @@ Route::add_processor_from_xml (const XMLNode& node, ProcessorList::iterator iter
 			} else if (prop->value() == "main-outs") {
 
 				if (_main_outs) {
-					if (_main_outs->set_state (node)) {
+					if (_main_outs->set_state (node, Stateful::loading_state_version)) {
 						return false;
 					} else {
 						return true;
@@ -848,11 +848,11 @@ Route::add_processor_from_xml_2X (const XMLNode& node, int version, ProcessorLis
 				    prop->value() == "vst" ||
 				    prop->value() == "audiounit") {
 					
-					processor.reset (new PluginInsert (_session, node, version));
+					processor.reset (new PluginInsert (_session, node));
 					
 				} else {
 					
-					processor.reset (new PortInsert (_session, _mute_master, node, version));
+					processor.reset (new PortInsert (_session, _mute_master, node));
 				}
 
 			}
@@ -1710,9 +1710,9 @@ Route::_set_state (const XMLNode& node, int version, bool /*call_base*/)
 			}
 
 			if (prop->value() == "Input") {
-				_input->set_state (*child);
+				_input->set_state (*child, version);
 			} else if (prop->value() == "Output") {
-				_output->set_state (*child);
+				_output->set_state (*child, version);
 			}
 		}
 
@@ -1815,7 +1815,7 @@ Route::_set_state (const XMLNode& node, int version, bool /*call_base*/)
 		} else if (child->name() == X_("Controllable") && (prop = child->property("name")) != 0) {
 
 			if (prop->value() == "solo") {
-				_solo_control->set_state (*child);
+				_solo_control->set_state (*child, version);
 				_session.add_controllable (_solo_control);
 			}
 
@@ -1827,7 +1827,7 @@ Route::_set_state (const XMLNode& node, int version, bool /*call_base*/)
 			}
 
 		} else if (child->name() == X_("MuteMaster")) {
-			_mute_master->set_state (*child);
+			_mute_master->set_state (*child, version);
 		}
 	}
 
@@ -1887,6 +1887,11 @@ Route::_set_state_2X (const XMLNode& node, int version)
 		child = *niter;
 
 		if (child->name() == IO::state_node_name) {
+
+			/* there is a note in IO::set_state_2X() about why we have to call
+			   this directly.
+			*/
+
 			_input->set_state_2X (*child, version, true);
 			_output->set_state_2X (*child, version, false);
 
@@ -2011,7 +2016,7 @@ Route::_set_state_2X (const XMLNode& node, int version)
 		} else if (child->name() == X_("Controllable") && (prop = child->property("name")) != 0) {
 			
 			if (prop->value() == "solo") {
-				_solo_control->set_state (*child);
+				_solo_control->set_state (*child, version);
 				_session.add_controllable (_solo_control);
 			} 
 
@@ -2144,7 +2149,7 @@ Route::set_processor_state (const XMLNode& node)
 
 			// and make it (just) so
 
-			(*i)->set_state (**niter);
+			(*i)->set_state (**niter, Stateful::current_state_version);
 		}
 	}
 
diff --git a/libs/ardour/send.cc b/libs/ardour/send.cc
index bd9eccaf54..5a39c3322a 100644
--- a/libs/ardour/send.cc
+++ b/libs/ardour/send.cc
@@ -167,7 +167,7 @@ Send::set_state (const XMLNode& node, int version)
 
 	/* XXX need to load automation state & data for amp */
 
-	Delivery::set_state (*insert_node);
+	Delivery::set_state (*insert_node, version);
 
 	return 0;
 }
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 79790b5673..d8c5639902 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -353,6 +353,10 @@ Session::destroy ()
 
 	delete state_tree;
 
+	/* reset dynamic state version back to default */
+	
+	Stateful::loading_state_version = 0;
+
 	terminate_butler_thread ();
 	//terminate_midi_thread ();
 
@@ -547,7 +551,7 @@ Session::when_engine_running ()
 
 			/* existing state for Click */
 
-			if (_click_io->set_state (*child->children().front()) == 0) {
+			if (_click_io->set_state (*child->children().front(), Stateful::loading_state_version) == 0) {
 
 				_clicking = Config->get_clicking ();
 
diff --git a/libs/ardour/session_command.cc b/libs/ardour/session_command.cc
index ffd68bb5a6..e7c9819d20 100644
--- a/libs/ardour/session_command.cc
+++ b/libs/ardour/session_command.cc
@@ -164,7 +164,7 @@ Session::GlobalRouteStateCommand::GlobalRouteStateCommand (Session& s, void* p)
 Session::GlobalRouteStateCommand::GlobalRouteStateCommand (Session& s, const XMLNode& node)
 	: sess (s), src (this)
 {
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor ();
 	}
 }
@@ -389,7 +389,7 @@ Session::GlobalMeteringStateCommand::GlobalMeteringStateCommand(Session &s, void
 Session::GlobalMeteringStateCommand::GlobalMeteringStateCommand (Session& s, const XMLNode& node)
 	: sess (s), src (this)
 {
-	if (set_state (node)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor();
 	}
 }
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index de99558c16..a0254fab6e 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -6,7 +6,7 @@
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
 
-  This program is distributed in the hope that it will be useful,
+ This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
@@ -311,7 +311,7 @@ Session::second_stage_init (bool new_session)
 	// to call setup_raid_path() here.
 
 	if (state_tree) {
-		if (set_state (*state_tree->root())) {
+		if (set_state (*state_tree->root(), Stateful::loading_state_version)) {
 			return -1;
 		}
 	} else {
@@ -756,7 +756,7 @@ int
 Session::restore_state (string snapshot_name)
 {
 	if (load_state (snapshot_name) == 0) {
-		set_state (*state_tree->root());
+		set_state (*state_tree->root(), Stateful::loading_state_version);
 	}
 
 	return 0;
@@ -824,20 +824,20 @@ Session::load_state (string snapshot_name)
 	}
 
 	const XMLProperty* prop;
-	bool is_old = false; // session is _very_ old (pre-2.0)
 
 	if ((prop = root.property ("version")) == 0) {
 		/* no version implies very old version of Ardour */
-		is_old = true;
+		Stateful::loading_state_version = 1000;
 	} else {
-		int major_version;
-		major_version = atoi (prop->value().c_str()); // grab just the first number before the period
-		if (major_version < 2) {
-			is_old = true;
-		}
-	}
+		int major;
+		int minor;
+		int micro;
 
-	if (is_old) {
+		sscanf (prop->value().c_str(), "%d.%d.%d", &major, &minor, &micro);
+		Stateful::loading_state_version = (major * 1000) + minor;
+	}
+		
+	if (Stateful::loading_state_version < CURRENT_SESSION_FILE_VERSION) {
 
 		sys::path backup_path(_session_dir->root_path());
 
@@ -1212,7 +1212,7 @@ Session::set_state (const XMLNode& node, int version)
 	if (version >= 3000) {
 		if ((child = find_named_node (node, "Metadata")) == 0) {
 			warning << _("Session: XML state has no metadata section") << endmsg;
-		} else if (_metadata->set_state (*child)) {
+		} else if (_metadata->set_state (*child, version)) {
 			goto out;
 		}
 	}
@@ -1220,7 +1220,7 @@ Session::set_state (const XMLNode& node, int version)
 	if ((child = find_named_node (node, "Locations")) == 0) {
 		error << _("Session: XML state has no locations section") << endmsg;
 		goto out;
-	} else if (_locations.set_state (*child)) {
+	} else if (_locations.set_state (*child, version)) {
 		goto out;
 	}
 
@@ -1331,7 +1331,7 @@ Session::set_state (const XMLNode& node, int version)
 	if ((child = find_named_node (node, "TempoMap")) == 0) {
 		error << _("Session: XML state has no Tempo Map section") << endmsg;
 		goto out;
-	} else if (_tempo_map->set_state (*child)) {
+	} else if (_tempo_map->set_state (*child, version)) {
 		goto out;
 	}
 
@@ -1345,7 +1345,7 @@ Session::set_state (const XMLNode& node, int version)
 	if ((child = find_named_node (node, "Click")) == 0) {
 		warning << _("Session: XML state has no click section") << endmsg;
 	} else if (_click_io) {
-		_click_io->set_state (*child);
+		_click_io->set_state (*child, version);
 	}
 
 	if ((child = find_named_node (node, "ControlProtocols")) != 0) {
@@ -1419,7 +1419,7 @@ Session::XMLRouteFactory (const XMLNode& node, int version)
 			return ret;
 		}
 	} else {
-		boost::shared_ptr<Route> ret (new Route (*this, node, version));
+		boost::shared_ptr<Route> ret (new Route (*this, node));
 		return ret;
 	}
 }
diff --git a/libs/ardour/smf_source.cc b/libs/ardour/smf_source.cc
index 358cbb1257..eb8d844949 100644
--- a/libs/ardour/smf_source.cc
+++ b/libs/ardour/smf_source.cc
@@ -75,7 +75,7 @@ SMFSource::SMFSource (Session& s, const XMLNode& node, bool must_exist)
 	, _last_ev_time_frames(0)
 	, _smf_last_read_end (0)
 {
-	if (set_state(node)) {
+	if (set_state(node, Stateful::loading_state_version)) {
 		throw failed_constructor ();
 	}
 
@@ -331,15 +331,15 @@ SMFSource::get_state ()
 int
 SMFSource::set_state (const XMLNode& node, int version)
 {
-	if (Source::set_state (node)) {
+	if (Source::set_state (node, version)) {
 		return -1;
 	}
 
-	if (MidiSource::set_state (node)) {
+	if (MidiSource::set_state (node, version)) {
 		return -1;
 	}
 
-	if (FileSource::set_state (node)) {
+	if (FileSource::set_state (node, version)) {
 		return -1;
 	}
 
diff --git a/libs/ardour/source.cc b/libs/ardour/source.cc
index 7ed4e584ce..fe8a8a1e0a 100644
--- a/libs/ardour/source.cc
+++ b/libs/ardour/source.cc
@@ -68,7 +68,7 @@ Source::Source (Session& s, const XMLNode& node)
 	_analysed = false;
 	_in_use = 0;
 
-	if (set_state (node) || _type == DataType::NIL) {
+	if (set_state (node, Stateful::loading_state_version) || _type == DataType::NIL) {
 		throw failed_constructor();
 	}
 
diff --git a/libs/ardour/tempo_map_importer.cc b/libs/ardour/tempo_map_importer.cc
index 1d37383fb5..1f9f518614 100644
--- a/libs/ardour/tempo_map_importer.cc
+++ b/libs/ardour/tempo_map_importer.cc
@@ -99,5 +99,5 @@ TempoMapImporter::_cancel_move ()
 void
 TempoMapImporter::_move ()
 {
-	session.tempo_map().set_state (xml_tempo_map);
+	session.tempo_map().set_state (xml_tempo_map, Stateful::current_state_version);
 }
diff --git a/libs/ardour/track.cc b/libs/ardour/track.cc
index ecd8208282..ce208769f6 100644
--- a/libs/ardour/track.cc
+++ b/libs/ardour/track.cc
@@ -51,8 +51,8 @@ Track::Track (Session& sess, string name, Route::Flag flag, TrackMode mode, Data
 	_mode = mode;
 }
 
-Track::Track (Session& sess, const XMLNode& node, int version, DataType default_type)
-	: Route (sess, node, version, default_type)
+Track::Track (Session& sess, const XMLNode& node, DataType default_type)
+	: Route (sess, node, default_type)
 	, _rec_enable_control (new RecEnableControllable(*this))
 {
 	_freeze_record.state = NoFreeze;
diff --git a/libs/ardour/user_bundle.cc b/libs/ardour/user_bundle.cc
index 73b5960e03..16ecb88c8d 100644
--- a/libs/ardour/user_bundle.cc
+++ b/libs/ardour/user_bundle.cc
@@ -15,10 +15,10 @@ ARDOUR::UserBundle::UserBundle (std::string const & n)
 
 }
 
-ARDOUR::UserBundle::UserBundle (XMLNode const & x, bool i)
+ARDOUR::UserBundle::UserBundle (XMLNode const & node, bool i)
 	: Bundle (i)
 {
-	if (set_state (x)) {
+	if (set_state (node, Stateful::loading_state_version)) {
 		throw failed_constructor ();
 	}
 }
diff --git a/libs/ardour/wscript b/libs/ardour/wscript
index fd71f2e6a7..3711d631fc 100644
--- a/libs/ardour/wscript
+++ b/libs/ardour/wscript
@@ -19,6 +19,9 @@ LIBARDOUR_VERSION = "%s.%s.%s" % (MAJOR, MINOR, MICRO)
 # micro increment <=> no interface changes
 LIBARDOUR_LIB_VERSION = '3.0.0'
 
+# default state file version for this build
+CURRENT_SESSION_FILE_VERSION = 3000
+
 # Variables for 'waf dist'
 APPNAME = 'libardour'
 VERSION = LIBARDOUR_VERSION
@@ -224,6 +227,8 @@ def configure(conf):
 	conf.define('HAVE_RUBBERBAND', 1) # controls whether we think we have it
 	conf.define('USE_RUBBERBAND', 1)  # controls whether we actually use it
 
+	conf.define('CURRENT_SESSION_FILE_VERSION', CURRENT_SESSION_FILE_VERSION)
+
 	conf.check(header_name='sys/vfs.h', define_name='HAVE_SYS_VFS_H')
 	conf.check(header_name='wordexp.h', define_name='HAVE_WORDEXP')