diff --git a/libs/ardour/midi_diskstream.cc b/libs/ardour/midi_diskstream.cc
index 8b047490e7..f45331a5b1 100644
--- a/libs/ardour/midi_diskstream.cc
+++ b/libs/ardour/midi_diskstream.cc
@@ -1323,6 +1323,7 @@ MidiDiskstream::use_new_write_source (uint32_t n)
 
 		if (_write_source->is_empty ()) {
 			_write_source->mark_for_remove ();
+			_write_source->drop_references ();
 			_write_source.reset();
 		} else {
 			_write_source.reset();
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 9cf48b7154..56e4660125 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -2424,6 +2424,7 @@ Session::add_source (boost::shared_ptr<Source> source)
 	}
 
 	if (result.second) {
+		source->DropReferences.connect_same_thread (*this, boost::bind (&Session::remove_source, this, boost::weak_ptr<Source> (source)));
 		set_dirty();
 	}