Index: t3lib/js/extjs/notifications.js
===================================================================
--- t3lib/js/extjs/notifications.js	(revision 9230)
+++ t3lib/js/extjs/notifications.js	(working copy)
@@ -168,7 +168,7 @@
 			var window = this.getById(id);
 			if (window) {
 				window.close();
-				windowCollection.remove(id);
+				windowCollection.remove(window);
 			}
 		},