Proxy cache of X-Accel-Redirect, how?

[bongtv]

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