diff --git a/libs/ardour/ardour/audioregion.h b/libs/ardour/ardour/audioregion.h
index 460d76b551..0776669874 100644
--- a/libs/ardour/ardour/audioregion.h
+++ b/libs/ardour/ardour/audioregion.h
@@ -197,7 +197,7 @@ class AudioRegion : public Region
 	PBD::Property<gain_t>   _scale_amplitude;
 	
 	void register_properties ();
-	void post_set ();
+	void post_set (const PBD::PropertyChange&);
 
 	void init ();
 	void set_default_fades ();
diff --git a/libs/ardour/ardour/midi_region.h b/libs/ardour/ardour/midi_region.h
index 53ffb4497c..650c7c9b2e 100644
--- a/libs/ardour/ardour/midi_region.h
+++ b/libs/ardour/ardour/midi_region.h
@@ -130,6 +130,7 @@ class MidiRegion : public Region
 			     MidiStateTracker* tracker = 0) const;
 
 	void register_properties ();
+        void post_set (const PBD::PropertyChange&);
 
 	void recompute_at_start ();
 	void recompute_at_end ();
diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index 5c213bfb7c..9de1de1279 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -224,7 +224,7 @@ AudioRegion::~AudioRegion ()
 }
 
 void
-AudioRegion::post_set ()
+AudioRegion::post_set (const PropertyChange& /*ignored*/)
 {
 	if (!_sync_marked) {
 		_sync_position = _start;
diff --git a/libs/ardour/midi_region.cc b/libs/ardour/midi_region.cc
index e487cae2f5..02d9f7d398 100644
--- a/libs/ardour/midi_region.cc
+++ b/libs/ardour/midi_region.cc
@@ -123,6 +123,14 @@ MidiRegion::clone ()
         return boost::dynamic_pointer_cast<MidiRegion> (RegionFactory::create (ms, plist, true));
 }
 
+void
+MidiRegion::post_set (const PropertyChange& pc)
+{
+        if (pc.contains (Properties::length) || pc.contains (Properties::position)) {
+                update_length_beats ();
+        }
+}
+
 void
 MidiRegion::set_length_internal (framecnt_t len)
 {