Setup: php5-fpm listening on socket + nginx 1.2.6

Wanted to use mod_auth_request for www authentication. Works fine for GET requests, POST requests time out with error 504.

Error log:
2013/02/24 00:13:03 [error] 24004#0: *13 auth request unexpected status: 504 while sending to client, client: 80.187.106.XXX, server: xxx.net, request: "POST /test.php HTTP/1.1", host: "xxx.net", referrer: "https://xxx.net/test.php"

With GET, as stated, and when testing the subrequest script directly, everything works fine. Gives 201/401 header, empty body as it should.

location ~ \.php$ {

root /var/www;

fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
fastcgi_intercept_errors on;
error_page 404 /index.html;

fastcgi_param DOCUMENT_ROOT /var/www;
fastcgi_param SCRIPT_FILENAME /var/www$fastcgi_script_name;
fastcgi_param PATH_TRANSLATED /var/www$fastcgi_script_name;

include /etc/nginx/fastcgi.conf;

auth_request /authenticator/www.php;
}

location = /authenitcator/www.php {
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_param SCRIPT_FILENAME /var/www$fastcgi_script_name;
fastcgi_param PATH_TRANSLATED /var/www$fastcgi_script_name;
}

Does anyone have an idea?

/refghbn