How to preserve request url with nginx proxy_pass

I was trying to use [Thin][1] app server and had one issue. When nginx [proxies][2] the request to Thin (or Unicorn) using `proxy_pass http://my_app_upstream;` the application receives the modified URL sent by nginx (`http://my_app_upstream`). What I want is to pass the original URL and the original request from client with no modification as the app relies heavily on it. The nginx' [doc][2] says: > If it is necessary to transmit URI in > the unprocessed form then directive > proxy_pass should be used without URI > part. But I don't understand how exactly to configure that as the related sample is actually using URI: location /some/path/ { proxy_pass http://127.0.0.1; } So could you please help me figuring out how to **preserve the original request URL** from the client? [1]: http://code.macournoyer.com/thin/ [2]: http://wiki.nginx.org/HttpProxyModule#proxy_pass