--- ck-get-x11-server-pid.c.old	2009-07-23 18:55:47.000000000 +0100
+++ ck-get-x11-server-pid.c	2010-02-04 18:10:21.105804521 +0000
@@ -45,10 +45,15 @@
         if (display_name == NULL) {
                 g_warning ("DISPLAY is not set");
                 exit (1);
         }
 
+        if (display_name[0] != ':' && g_strrstr(display_name, ":") != NULL) {
+                g_warning ("DISPLAY is not a UNIX domain socket, can't get PID");
+                exit (1);
+        }
+
         xdisplay = XOpenDisplay (display_name);
         if (xdisplay == NULL) {
                 g_warning ("cannot open display: %s", display_name ? display_name : "");
                 exit (1);
         }