diff --git a/gtk2_ardour/ardour_knob.cc b/gtk2_ardour/ardour_knob.cc
index 1cad9f4f55..e7d9647d3b 100644
--- a/gtk2_ardour/ardour_knob.cc
+++ b/gtk2_ardour/ardour_knob.cc
@@ -377,10 +377,12 @@ ArdourKnob::set_controllable (boost::shared_ptr<Controllable> c)
 void
 ArdourKnob::controllable_changed ()
 {
-	_val = binding_proxy.get_controllable()->get_interface();  //% of knob travel
+	boost::shared_ptr<PBD::Controllable> c = binding_proxy.get_controllable();
 
+	_val = c->get_interface();  //% of knob travel
 	_val = min( max(0.0f, _val), 1.0f);  //range check
 
+	ARDOUR_UI::instance()->set_tip (*this, _tooltip_prefix + c->get_user_string());
 	set_dirty();
 }
 
diff --git a/gtk2_ardour/ardour_knob.h b/gtk2_ardour/ardour_knob.h
index 3a9c2bd7ff..50fc81bfaa 100644
--- a/gtk2_ardour/ardour_knob.h
+++ b/gtk2_ardour/ardour_knob.h
@@ -53,6 +53,8 @@ public:
 	void add_elements (Element);
 	static Element default_elements;
 
+	void set_tooltip_prefix (std::string pfx) { _tooltip_prefix = pfx; }
+
 	boost::shared_ptr<PBD::Controllable> get_controllable() { return binding_proxy.get_controllable(); }
  	void set_controllable (boost::shared_ptr<PBD::Controllable> c);
 
@@ -91,6 +93,8 @@ public:
 	void action_sensitivity_changed ();
 	void action_visibility_changed ();
 	void action_tooltip_changed ();
+
+	std::string _tooltip_prefix;
 };
 
 #endif /* __gtk2_ardour_ardour_knob_h__ */