Proxy cache of X-Accel-Redirect, how? (no replies)

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?