Changing Alternate Access Mapping

I'm not sure if anyone else has come across this, but I thought I would put it in my blog. If you go through Central Admin and modify an existing Alternate Access Mapping, it doesn't modify the Host Header in IIS. eg, if for Custom you had it pointing to http://web1 and the new one is http://web2, the host header for that site in IIS will still point the web1 and when a user hits web2, they will hit the default website. Simply modify the host hear to also accept web2 and problem solved.