diff --git a/tools/dbus-launch.c b/tools/dbus-launch.c
index 7ecee63..13e7235 100644
--- a/tools/dbus-launch.c
+++ b/tools/dbus-launch.c
@@ -406,6 +406,7 @@ static pid_t bus_pid_to_kill = -1;
 static void
 kill_bus(void)
 {
+  if (bus_pid_to_kill == -1) return;
   verbose ("Killing message bus and exiting babysitter\n");
   kill (bus_pid_to_kill, SIGTERM);
   sleep (3);
@@ -1273,7 +1274,9 @@ main (int argc, char **argv)
 	  exit (1);
 	}
 
-      bus_pid = val;
+      /* Have to initialize bus_pid_to_kill ASAP, so that the
+         X error callback can kill it if an error happens. */
+      bus_pid_to_kill = bus_pid = val;
 
       close (bus_pid_to_launcher_pipe[READ_END]);
 
@@ -1291,7 +1294,6 @@ main (int argc, char **argv)
                 {
                   char *address = NULL;
                   /* another window got added. Return its address */
-                  bus_pid_to_kill = bus_pid;
                   if (x11_get_address (&address, &bus_pid, &wid)
                        && address != NULL)
                     {