diff --git a/gtk2_ardour/processor_box.cc b/gtk2_ardour/processor_box.cc
index e72e5c6723..c3694e73d4 100644
--- a/gtk2_ardour/processor_box.cc
+++ b/gtk2_ardour/processor_box.cc
@@ -4720,6 +4720,7 @@ void
 ProcessorWindowProxy::processor_going_away ()
 {
 	gui_connections.drop_connections ();
+	_unmap_connection.disconnect ();
 	delete _window;
 	_window = 0;
 	WM::Manager::instance().remove (this);
@@ -4777,7 +4778,9 @@ ProcessorWindowProxy::get (bool create)
 	if (_window && (is_custom != want_custom)) {
 		/* drop existing window - wrong type */
 		set_state_mask (Gtkmm2ext::WindowProxy::StateMask (state_mask () & ~WindowProxy::Size));
+		_unmap_connection.block ();
 		drop_window ();
+		_unmap_connection.unblock ();
 	}
 
 	if (!_window) {