diff --git a/src/cpp/ripple/Application.h b/src/cpp/ripple/Application.h
index 2a848ed7c5..c8492e02a4 100644
--- a/src/cpp/ripple/Application.h
+++ b/src/cpp/ripple/Application.h
@@ -149,6 +149,13 @@ public:
 	void run();
 	void stop();
 	void sweep();
+
+#ifdef DEBUG
+	void mustHaveMasterLock()		{ bool tl = mMasterLock.try_lock(); assert(tl); mMasterLock.unlock(); }
+#else
+	void mustHaveMasterLock()		{ ; }
+#endif
+
 };
 
 extern Application* theApp;