Problem with mod_rewrite/mod_proxy while using Passenger 2.2.7

[Carsten Gehling]

After upgrading passenger from 2.2.0 to 2.2.7, I have suddenly run
into some problems with a couple of rewrite rules, that worked before
the upgrade.

I have this in my virtualhost config:
----------------------------------------------
RewriteEngine On

RewriteLog /var/log/apache2/rewrite
RewriteLogLevel 9

RewriteRule ^/pdf/(\d+)_(\d+)\.pdf http://edward.biq.dk/pdf/$1_$2.pdf
[P,L]
----------------------------------------------

When checking the rewrite-logfile, everything seems in order:
----------------------------------------------
87.104.32.55 - - [04/Jan/2010:09:45:51 +0100] [www.biq.dk/sid#81cdc70]
[rid#82986f0/initial] (2) init rewrite engine with requested uri /pdf/
215198_769.pdf
87.104.32.55 - - [04/Jan/2010:09:45:51 +0100] [www.biq.dk/sid#81cdc70]
[rid#82986f0/initial] (3) applying pattern '^/pdf/(\d+)_(\d+)\.pdf' to
uri '/pdf/215198_769.pdf'
87.104.32.55 - - [04/Jan/2010:09:45:51 +0100] [www.biq.dk/sid#81cdc70]
[rid#82986f0/initial] (2) rewrite '/pdf/215198_769.pdf' -> 'http://
edward.biq.dk/pdf/215198_769.pdf'
87.104.32.55 - - [04/Jan/2010:09:45:51 +0100] [www.biq.dk/sid#81cdc70]
[rid#82986f0/initial] (2) forcing proxy-throughput with
http://edward.biq.dk/pdf/215198_769.pdf
87.104.32.55 - - [04/Jan/2010:09:45:51 +0100] [www.biq.dk/sid#81cdc70]
[rid#82986f0/initial] (1) go-ahead with proxy request proxy:http://
edward.biq.dk/pdf/215198_769.pdf [OK]
----------------------------------------------

BUT the rewritten request is never proxied over to the other server
(edward.biq.dk).

I suspect that this problem lies solely between passenger and
mod_proxy, but I haven't been able to Google any good answers.

What has happened between these versions?

BTW: I have just tried with Passenger 2.2.8 - the problem is still
there.

- Carsten