Index: clipboard.c
===================================================================
--- win32ss/user/ntuser/clipboard.c	(revision 74970)
+++ win32ss/user/ntuser/clipboard.c	(working copy)
@@ -709,7 +709,7 @@
     UserEnterShared();
 
     /* If the format is built-in we fail */
-    if (fmt < 0xc000)
+    if (fmt < 0xc000 || fmt > 0xffff)
     {
         /* Registetrated formats are >= 0xc000 */
         goto cleanup;