--- a/mercurial/dispatch.py	Mon Nov 07 03:14:53 2011 +0100
+++ b/mercurial/dispatch.py	Mon Nov 07 03:14:53 2011 +0100
@@ -24,7 +24,7 @@
 
 def run():
     "run the command in sys.argv"
-    sys.exit(dispatch(request(sys.argv[1:])))
+    sys.exit((dispatch(request(sys.argv[1:])) or 0) & 255)
 
 def dispatch(req):
     "run the command specified in req.args"