diff --git a/ChangeLog b/ChangeLog
index 814ee19..68d6e27 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2004-11-23  Ross Burton  <ross@burtonini.com>
+
+	* src/util.c: Check the xterm window ID is valid for the current
+	display before trying to use it.
+
 2004-10-30  Francisco Javier F. Serrador  <serrador@cvs.gnome.org>
 
 	* src/main.c: Typo fixing: Notication options --> Notification options
diff --git a/src/util.c b/src/util.c
index 6e9de2a..ff7d18b 100644
--- a/src/util.c
+++ b/src/util.c
@@ -272,8 +272,16 @@ transient_get_xterm (void)
   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;
 }