SetOutputFilter doesn't work in <Location>s?

Hi,

I have a long-standing problem with getting Apache 2 output filters to
work on a per-<Location> basis. As far as I can tell, the
SetOutputFilter directive either doesn't work in <Location> blocks, or
is quite unpredictable in that context. Here's a test configuration:

<VirtualHost 80.68.95.15:80>
ServerAdmin webmaster@insectnation.org
DocumentRoot /www/filtertest
ServerName test.insectnation.org

#SetOutputFilter a;b

<Location />
Options Indexes FollowSymLinks MultiViews ExecCGI
AllowOverride None
Order allow,deny
Allow from all
DirectoryIndex index
</Location>

ExtFilterDefine a mode=output intype=text/html outtype=text/html
cmd="/bin/sed -e s/foo/bar/g"
ExtFilterDefine b mode=output intype=text/html outtype=text/html
cmd="/bin/sed -e s/bing/boom/g"
<Location /a>
SetOutputFilter a
</Location>
<Location /b>
SetOutputFilter b
#Order deny,allow
#Deny from all
</Location>
</VirtualHost>

The results of using this configuration are as follows:

* The sed replacements take place neither in test.insectnation.org/a
or test.insectnation.org/b
* If the Location /b access is denied (by uncommenting the Order and
Deny statements), this is correctly reflected in the browser behaviour
* If the SetOutputFilter at VirtualHost level (i.e not in any
Location blocks) is uncommented, the sed replacements both take place
as expected

So, the problem is not the Location matching because the access denial
works as expected: there seems to be some problem specifically with
SetOutputFilter used on a Location basis. This is observed using Apache
2.0.55 as packaged in Ubuntu Dapper:

andy@dirac:~$ apache2 -v
Server version: Apache/2.0.55
Server built: May 29 2006 01:52:53

I've also observed the same behaviour in Scientific Linux 4.x. Can
anyone offer any suggestions / try this config for themselves and
comment. If it's a genuine problem then it should be reported as a bug,
but I'm not aware of any independent confirmations: a similar post to
this on the Apache users@httpd mailing list elicited no responses :-(

Cheers,
Andy