url_for and routes with host

I have a route the looks like this:

map.preview_profile '/profile/:client/:profile', :controller =>
'profiles', :action => 'pub_view'

if I do url_for(:controller => 'profiles', :action =>
'pub_view', :client => 'client-xyz', :profile => 'profile1' )

I get this: "/profile/client-xyz/profile1"

However, if I change my route to this:

map.preview_profile '/profile/:client/:profile', :controller =>
'profiles', :action => 'pub_view', :host => 'www.example.com'
(I added the :host option)
the same url_for returns this:

/profiles/pub_view?client_permalink=client-
xyz&profile_permalink=profile1

I've also tried
url_for(:host => 'www.example.com', :controller => 'profiles', :action
=> 'pub_view', :client => 'client-xyz', :profile => 'profile1' )

with the same results.

So my conclusion is that Routes and URL generation is broken if you
specify a :host in the Route. Is that correct?

FWIW, I'm not really doing url_for, I'm trying to use expire_page but
that relies on url_for.

Thanks for any help or work-arounds for this issue.

Eric Lund