routing error: uninitialized constant Users::OmniauthCallbacksController

Question

I create application using rails4 with devise and omniauth am trying facebook integration. Am login with facebook initially its login and authenticated the credential, after the callback its redirect to my application and through's

Routing error: uninitialized constant Users::OmniauthCallbacksController

i show my code related to devise fb

config/intializers/devise.rb

require "omniauth-facebook"
  config.secret_key = 'ef8c3900aebe5cc02feb1dfafb084b2ed35412b43b9424315ac192336f3d16389449739f9a4d451621a912be899af0b9d1ce66fde56487e7edda30ba3997a2cd'
  config.omniauth :facebook, '############', '######################', :strategy_class => OmniAuth::Strategies::Facebook

config/routes.rb devise_for :users, controllers: {omniauth_callbacks: "users/omniauth_callbacks"}

  devise_scope :user do
    get 'sign_in', :to => 'devise/sessions#new'
    get 'sign_out', :to => 'devise/sessions#destroy'
    root to: "devise/sessions#new"
  end

and my view/layout/application.html.erb (for fb script)

<div id="fb-root"></div>
    <script>
      window.fbAsyncInit = function() {
        // init the FB JS SDK
        FB.init({
          appId      : '##########',                        // App ID from the app dashboard
          channelUrl : 'http://localhost:3000/channel.html', // Channel file for x-domain comms
          status     : true,                                 // Check Facebook Login status
          xfbml      : true                                  // Look for social plugins on the page
        });


        // Additional initialization code such as adding Event Listeners goes here
      };

      // Load the SDK asynchronously
      (function(d, s, id){
         var js, fjs = d.getElementsByTagName(s)[0];
         if (d.getElementById(id)) {return;}
         js = d.createElement(s); js.id = id;
         js.src = "//connect.facebook.net/en_US/all.js";
         fjs.parentNode.insertBefore(js, fjs);
       }(document, 'script', 'facebook-jssdk'));
    </script>

i tried many times but am getting the same error plz give your valuable solutions for this issue

Thanks in advance.