diff --git a/src/event.js b/src/event.js
index 299f71615..f3335a074 100644
--- a/src/event.js
+++ b/src/event.js
@@ -355,7 +355,7 @@ jQuery.event = {
 	dispatch: function( event ) {
 
 		// Make a writable jQuery.Event from the native event object
-		event = jQuery.event.fix( event || window.event );
+		event = jQuery.event.fix( event );
 
 		var i, j, cur, ret, selMatch, matched, matches, handleObj, sel,
 			handlers = ( (jQuery._data( this, "events" ) || {} )[ event.type ] || []),