diff --git a/lib/devise.rb b/lib/devise.rb
index f4492dbc65..022f2680d2 100644
--- a/lib/devise.rb
+++ b/lib/devise.rb
@@ -17,6 +17,7 @@ module Devise
   autoload :TokenGenerator,     'devise/token_generator'
 
   module Controllers
+    autoload :Generator,        'devise/controllers/generator'
     autoload :Helpers,          'devise/controllers/helpers'
     autoload :Rememberable,     'devise/controllers/rememberable'
     autoload :ScopedViews,      'devise/controllers/scoped_views'
@@ -294,7 +295,7 @@ def self.#{method}=(val)
 
   # If within the same application, Devise is to be mounted on different engines.
   mattr_accessor :controller_scopes
-  @@controller_scopes = :devise
+  @@controller_scopes = [:devise]
 
   # Default way to setup Devise. Run rails generate devise_install to create
   # a fresh initializer with all configuration values.
diff --git a/lib/devise/controllers/helpers.rb b/lib/devise/controllers/helpers.rb
index a0ea0edf24..e995423ad2 100644
--- a/lib/devise/controllers/helpers.rb
+++ b/lib/devise/controllers/helpers.rb
@@ -79,7 +79,7 @@ def warden
       #
       #   before_filter :my_filter, :unless => :devise_controller?
       def devise_controller?
-        is_a?(DeviseController)
+        self.class.included_modules.include?(::Devise::Mixins::Base)
       end
 
       # Setup a param sanitizer to filter parameters using strong_parameters. See
diff --git a/lib/devise/mailers/helpers.rb b/lib/devise/mailers/helpers.rb
index 06cd4b42de..b0f8825d02 100644
--- a/lib/devise/mailers/helpers.rb
+++ b/lib/devise/mailers/helpers.rb
@@ -60,6 +60,7 @@ def mailer_sender(mapping, sender = :from)
 
       def template_paths
         template_path = _prefixes.dup
+        template_path.unshift "#{Devise.router_name}/devise/mailer"   if Devise.router_name
         template_path.unshift "#{@devise_mapping.scoped_path}/mailer" if self.class.scoped_views?
         template_path
       end
diff --git a/lib/devise/rails.rb b/lib/devise/rails.rb
index 70e79f84ac..d75c5c5058 100644
--- a/lib/devise/rails.rb
+++ b/lib/devise/rails.rb
@@ -13,6 +13,13 @@ class Engine < ::Rails::Engine
     # Force routes to be loaded if we are doing any eager load.
     config.before_eager_load { |app| app.reload_routes! }
 
+    # Generate the Devise's Controllers (per request for development & once for production) for all the specified controller_scopes.
+    config.to_prepare do
+      Devise.controller_scopes.each do |scope|
+        Devise::Controllers::Generator.generate scope
+      end
+    end
+
     initializer "devise.url_helpers" do
       Devise.include_helpers(Devise::Controllers)
     end