Rails3 I18n locale in urls

As per the Rails 3 I18N documentation, I wrote in my routes.rb

scope "(/:locale)", :locale => /en|nl/ do
    resources :users
end
match '/:locale' => 'home#index'
root :to => "home#index"

and in my ApplicationController.rb
before_filter :set_locale
  def set_locale
    I18n.locale = params[:locale]
  end
  def self.default_url_options(options={})
    {:locale => I18n.locale}
  end

but I sill get urls with the locale parameter as if the scope was
ignored ...

http://localhost:3000/users/sign_in?locale=en

I rather should get : http://localhost:3000/en/users/sign_in

( I am using also Devise 1.2...)

what could be wrong ? thanks for your suggestions

the clue was in my question ..... I am using Devise .. so I should
scope the devise for :

  scope "(:locale)", :locale => /en|nl/ do
      devise_for :users .....
  end