diff --git a/gtk2_ardour/public_editor.h b/gtk2_ardour/public_editor.h
index ce0e81a650..7961d64e38 100644
--- a/gtk2_ardour/public_editor.h
+++ b/gtk2_ardour/public_editor.h
@@ -123,7 +123,7 @@ public:
 	virtual ~PublicEditor ();
 
 	/** @return Singleton PublicEditor instance */
-	static PublicEditor& instance () { return *_instance; }
+	static PublicEditor& instance () { assert (_instance); return *_instance; }
 
 	virtual bool have_idled() const = 0;
 	virtual void first_idle() = 0;