diff --git a/gtk2_ardour/trigger_master.h b/gtk2_ardour/trigger_master.h
index fa737f933a..16796d6ee8 100644
--- a/gtk2_ardour/trigger_master.h
+++ b/gtk2_ardour/trigger_master.h
@@ -59,7 +59,7 @@ private:
 	float _fraction;
 };
 
-class TriggerMaster : public ArdourCanvas::Rectangle
+class TriggerMaster : public ArdourCanvas::Rectangle, public sigc::trackable
 {
 public:
 	TriggerMaster (ArdourCanvas::Item* canvas);