[SQU] Forwarding all requests for a particular domain to another proxy

I have a setup with two squid proxies (2.3.STABLE4), where only one of
them (proxy1) is able to reach a particular domain (xyz.dk). I have
tried to configure the other proxy (proxy2) to forward all requests for
xyz.dk (and only these) to proxy1 with the following configuration
directives:

cache_peer proxy1 sibling 3128 3130 proxy-only
neighbor_type_domain proxy1 parent .xyz.dk
acl xyz dstdomain .xyz.dk
never_direct allow xyz
prefer_direct off

But this doesn't work - whenever I try to retrieve anything from xyz.dk
through proxy2, I get the following error:

--
While trying to retrieve the URL: http://www.xyz.dk/ 
The following error was encountered: 
     Valid document was not found in the cache and only-if-cached
directive was specified. 
You have issued a request with a only-if-cached cache control directive.
The document was not found in the cache, or it required revalidation
prohibited by only-if-cached directive.
--
If I change the cache_peer line to "cache_peer proxy1 parent 3128 3130
proxy-only" (and remove the neighbor_type_domain, acl, and never_direct
directives abov), all requests for xyz.dk is sent through proxy1, but so
are all other requests, and that is not what we want. Am I doing
something wrong, or is the neighbor_type_domain not working?
Regards,
Anders K. Pedersen
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