Index: dll/win32/ieframe/events.c
===================================================================
--- dll/win32/ieframe/events.c	(revision 67544)
+++ dll/win32/ieframe/events.c	(working copy)
@@ -327,7 +327,8 @@
     }
 
     This->sinks[i] = disp;
-    *pdwCookie = i+1;
+    if (pdwCookie)
+        *pdwCookie = i+1;
 
     return S_OK;
 }