nginx returns 503 when it gets 403 from haproxy

[CJ Ess]

In my environment I have Nginx terminating connections, then sending them
to an HAProxy upstream. We've noticed that whenever HAProxy emts a 403
error (Forbidden, in response to our ACL rules), NGINX reports a 503 result
(service unavailable) and I believe is logging an "upstream prematurely
closed connection while reading response header from upstream" error
message in the nginx error log.

What I'd really like to do is pass the 403 code back to the user - what do
I need to do?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.nginx.org/pipermail/nginx/attachments/20160414/3394cb0a/attachment.html>