Proxy cache of X-Accel-Redirect, how?

Hi!
Tried to cache the X-Accel-Redirect responses from Phusion Passenger
application server with the use of a second layer without success
(followed
the hint on http://forum.nginx.org/read.php?2,241734,241948#msg-241948).

Configuration:

  1. Application server (Phusion Passenger)
    adds X-Accel-Redirect header to response
    sends to

  2. NGINX server
    >> tries to cache <<
    proxy_ignore_headers X-Accel-Redirect;
    proxy_pass_header X-Accel-Redirect;
    passenger_pass_header X-Accel-Redirect;

      sends to
    
  3. NGINX server
    delivers file

But caching of the reuest on server (2) does not work.
Any idea?

Posted at Nginx Forum:
http://forum.nginx.org/read.php?2,256327,256327#msg-256327