diff --git a/src/mac/carbon/app.cpp b/src/mac/carbon/app.cpp
index 7c82e31a6e..bcf9cfb1d1 100644
--- a/src/mac/carbon/app.cpp
+++ b/src/mac/carbon/app.cpp
@@ -1124,6 +1124,9 @@ void wxApp::MacHandleOneEvent( WXEVENTREF evr )
         MacHandleUnhandledEvent(evr);
     }
     wxMacProcessNotifierAndPendingEvents() ;
+#if wxUSE_THREADS
+    wxMutexGuiLeaveOrEnter();
+#endif // wxUSE_THREADS
 }
 
 long wxMacTranslateKey(unsigned char key, unsigned char code) ;