Upstream: http_403 support in proxy_next_upstream (and friends). The parameter is mostly identical to http_404, and is expected to be used in similar situations. The 403 code might be returned by a backend instead of 404 on initial sync of new directories with rsync. See here for feature request and additional details: http://mailman.nginx.org/pipermail/nginx-ru/2013-April/050920.html