Rails 2.1 and map.root

I moved my project from rails 2.0 to 2.1 and map.root stop working:
It means if I have e.g:
    map.root :controller => 'sessions', :action => 'new'
it not working,
but when I try do this
   map.new_session :controller => 'sessions', :action => 'new'
   map.root :new_session
I have error:
/usr/lib/ruby/gems/1.8/gems/actionpack-2.1.0/lib/action_controller/routing/builder.rb:197:in
`build': Illegal route: the :controller must be specified!
(ArgumentError)

any ideas?

Sorry:

it works: map.root :controller => 'sessions', :action => 'new'

but this:

map.new_session :controller => 'sessions', :action => 'new'
map.root :new_session

not working, but in rails 2.1 it should....

any ideas?