How to use i18n_routing gem with rails2

Question

Hello all,

I installed the following gems in addition to rails 2.3.5:

i18n (0.4.1)
i18n_routing (0.3.7)

In environment.rb I added require i18n_routing

Inserted the following lines in routes.rb:

map.localized(I18n.available_locales, :verbose => true) do
  map.resources :users
  map.resource  :contact
end

but when I restart the server I got the following error:

/usr/local/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/routing/route_set.rb:56:in `method_missing': undefined method `localized' for # (NoMethodError)
from /public_html/config/routes.rb:14

what is going wrong? thanks