yum.postgresql.org 404 when port in host header

I'm debugging a chef bug [1] that was reported with a recent release
where requests are failing to yum.postgresql.rog now because the host
header includes a port. I'd like to narrow this down to a webserver,
configuration, or load balancer. Anyone here familiar with this server
and have any ideas?

This works fine:
curl -H Host:yum.postgresql.org
http://yum.postgresql.org/9.1/redhat/rhel-5-x86_64/pgdg-centos91-9.1-4.noarch.rpm

This returns a 404:
curl -H Host:yum.postgresql.org:80
http://yum.postgresql.org/9.1/redhat/rhel-5-x86_64/pgdg-centos91-9.1-4.noarch.rpm

Bryan

[1] https://tickets.opscode.com/browse/CHEF-5010