diff --git a/gtk2_ardour/ardour3_ui_default.conf b/gtk2_ardour/ardour3_ui_default.conf
index 42f5741e4d..8525908cf0 100644
--- a/gtk2_ardour/ardour3_ui_default.conf
+++ b/gtk2_ardour/ardour3_ui_default.conf
@@ -7,7 +7,7 @@
     <Option name="waveform" value="000000cc"/>
     <Option name="clipped waveform" value="ff0000e5"/>
     <Option name="region base" value="bfbfc1aa"/>
-    <Option name="selected region base" value="b591a8ff"/>
+    <Option name="selected region base" value="565693a6"/>
     <Option name="midi frame base" value="698f9d6d"/>
     <Option name="audio track base" value="c6d3d868"/>
     <Option name="audio bus base" value="dbd1ea68"/>
diff --git a/libs/ardour/ardour/midi_source.h b/libs/ardour/ardour/midi_source.h
index 433e7ceee9..c83debec3d 100644
--- a/libs/ardour/ardour/midi_source.h
+++ b/libs/ardour/ardour/midi_source.h
@@ -76,6 +76,8 @@ class MidiSource : public Source
 	
 	XMLNode& get_state ();
 	int set_state (const XMLNode&);
+	
+	bool length_mutable() const { return true; }
 
 	virtual void load_model(bool lock=true, bool force_reload=false) = 0;
 	virtual void destroy_model() = 0;
diff --git a/libs/ardour/ardour/source.h b/libs/ardour/ardour/source.h
index 869111bb07..aa8bc0ca1f 100644
--- a/libs/ardour/ardour/source.h
+++ b/libs/ardour/ardour/source.h
@@ -63,7 +63,8 @@ class Source : public SessionObject
 	XMLNode& get_state ();
 	int set_state (const XMLNode&);
 	
-	virtual bool destructive() const { return false; }
+	virtual bool destructive()    const { return false; }
+	virtual bool length_mutable() const { return false; }
 	
 	void use () { _in_use++; }
 	void disuse () { if (_in_use) { _in_use--; } }
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index 0505985aea..6d92c0bc88 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -1310,7 +1310,7 @@ Region::source_equivalent (boost::shared_ptr<const Region> other) const
 bool
 Region::verify_length (nframes_t len)
 {
-	if (source() && source()->destructive()) {
+	if (source() && (source()->destructive() || source()->length_mutable())) {
 		return true;
 	}
 
@@ -1328,7 +1328,7 @@ Region::verify_length (nframes_t len)
 bool
 Region::verify_start_and_length (nframes_t new_start, nframes_t& new_length)
 {
-	if (source() && source()->destructive()) {
+	if (source() && (source()->destructive() || source()->length_mutable())) {
 		return true;
 	}
 
@@ -1346,7 +1346,7 @@ Region::verify_start_and_length (nframes_t new_start, nframes_t& new_length)
 bool
 Region::verify_start (nframes_t pos)
 {
-	if (source() && source()->destructive()) {
+	if (source() && (source()->destructive() || source()->length_mutable())) {
 		return true;
 	}
 
@@ -1361,7 +1361,7 @@ Region::verify_start (nframes_t pos)
 bool
 Region::verify_start_mutable (nframes_t& new_start)
 {
-	if (source() && source()->destructive()) {
+	if (source() && (source()->destructive() || source()->length_mutable())) {
 		return true;
 	}