--- zenity-2.8.2.orig/src/util.c	2004-12-07 20:49:41.000000000 +0000
+++ zenity-2.8.2/src/util.c	2004-12-21 10:37:52.000000000 +0000
@@ -275,8 +275,16 @@
   if (wid_str) {
     char *wid_str_end;
     Window wid = strtoul (wid_str, &wid_str_end, 10);
-    if (*wid_str != '\0' && *wid_str_end == '\0' && wid != 0)
+    if (*wid_str != '\0' && *wid_str_end == '\0' && wid != 0) {
+      XWindowAttributes attrs;
+      gdk_error_trap_push ();
+      XGetWindowAttributes (GDK_DISPLAY(), wid, &attrs);
+      gdk_flush();
+      if (gdk_error_trap_pop () != 0) {
+        return None;
+      }
       return wid;
+    }
   }
   return None;
 }