Fixed returned value handling from the cookie rewrite handler. If the "proxy_cookie_domain" or "proxy_cookie_path" directive is used and there are no matches in Set-Cookie header then ngx_http_proxy_rewrite_cookie() returns NGX_DECLINED to indicate that the header was not rewritten. Returning this value further from the upstream headers copy handler resulted in 500 error response. See here for report: http://mailman.nginx.org/pipermail/nginx/2012-May/033858.html