diff --git a/src/mac/carbon/app.cpp b/src/mac/carbon/app.cpp
index f92a72d827..bee3132deb 100644
--- a/src/mac/carbon/app.cpp
+++ b/src/mac/carbon/app.cpp
@@ -475,7 +475,7 @@ pascal OSStatus wxMacAppEventHandler( EventHandlerCallRef handler , EventRef eve
             result = wxMacAppMenuEventHandler( handler , event , data ) ;
             break ;
         case kEventClassMouse :
-            result = wxMacTopLevelMouseEventHandler( handler , event , data ) ;
+            result = wxMacTopLevelMouseEventHandler( handler , event , NULL ) ;
             break ;
         case kEventClassAppleEvent :
             {