Rails 4 OmniAuth-Facebook request.env return nil

I have an application that uses Rails 4, OmniAuth and OmniAuth-facebook and in the controller action "request.env['omniauth.auth']" is nil.

GemFile

gem 'omniauth'
gem 'omniauth-facebook' # Facebook authentication
gem 'omniauth-twitter' #twitter authentication
gem "koala", "~> 1.10.0rc" # Facebook API
...

config/initializers/omniauth.rb

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :facebook, FACEBOOK_CONFIG['app_id'].to_s, FACEBOOK_CONFIG['secret'].to_s, {:scope => 'xmpp_login'}
  provider :twitter, '8v3vAAc0k878b#######'
end

Controller:

class SomeController
  def index
    raise env["omniauth.auth"].inspect
  end
...

The result is simply: 'nil'

What is missing?