diff --git a/lib/devise.rb b/lib/devise.rb
index c3bcdc9f..02a44eee 100644
--- a/lib/devise.rb
+++ b/lib/devise.rb
@@ -16,6 +16,7 @@ module Devise
     autoload :InternalHelpers, 'devise/controllers/internal_helpers'
     autoload :Rememberable, 'devise/controllers/rememberable'
     autoload :ScopedViews, 'devise/controllers/scoped_views'
+    autoload :SharedHelpers, 'devise/controllers/shared_helpers'
     autoload :UrlHelpers, 'devise/controllers/url_helpers'
   end
 
diff --git a/lib/devise/controllers/internal_helpers.rb b/lib/devise/controllers/internal_helpers.rb
index 86ad80db..92278665 100644
--- a/lib/devise/controllers/internal_helpers.rb
+++ b/lib/devise/controllers/internal_helpers.rb
@@ -6,19 +6,7 @@ module Devise
     module InternalHelpers #:nodoc:
       extend ActiveSupport::Concern
       include Devise::Controllers::ScopedViews
-
-      MIME_REFERENCES = Mime::HTML.respond_to?(:ref)
-
-      # Helper used by FailureApp and Devise controllers to retrieve proper formats.
-      def self.request_format(request)
-        if request.format.respond_to?(:ref)
-          request.format.ref
-        elsif MIME_REFERENCES
-          request.format
-        elsif request.format # Rails < 3.0.4
-          request.format.to_sym
-        end
-      end
+      include Devise::Controllers::SharedHelpers
 
       included do
         helper DeviseHelper
@@ -65,10 +53,6 @@ module Devise
 
     protected
 
-      def request_format
-        @request_format ||= Devise::Controllers::InternalHelpers.request_format(request)
-      end
-
       # Checks whether it's a devise mapped resource or not.
       def is_devise_resource? #:nodoc:
         unknown_action! <<-MESSAGE unless devise_mapping
@@ -81,11 +65,6 @@ Maybe you forgot to wrap your route inside the scope block? For example:
 MESSAGE
       end
 
-      # Check whether it's navigational format, such as :html or :iphone, or not.
-      def is_navigational_format?
-        Devise.navigational_formats.include?(request_format)
-      end
-
       # Returns real navigational formats which are supported by Rails
       def navigational_formats
         @navigational_formats ||= Devise.navigational_formats.select{ |format| Mime::EXTENSION_LOOKUP[format.to_s] }
diff --git a/lib/devise/controllers/shared_helpers.rb b/lib/devise/controllers/shared_helpers.rb
new file mode 100644
index 00000000..cf0954b8
--- /dev/null
+++ b/lib/devise/controllers/shared_helpers.rb
@@ -0,0 +1,26 @@
+module Devise
+  module Controllers
+    # Helpers used in both FailureApp and Devise controllers.
+    module SharedHelpers
+      MIME_REFERENCES = Mime::HTML.respond_to?(:ref)
+
+      protected
+
+      # Helper used by FailureApp and Devise controllers to retrieve proper formats.
+      def request_format
+        @request_format ||= if request.format.respond_to?(:ref)
+          request.format.ref
+        elsif MIME_REFERENCES
+          request.format
+        elsif request.format # Rails < 3.0.4
+          request.format.to_sym
+        end
+      end
+
+      # Check whether it's navigational format, such as :html or :iphone, or not.
+      def is_navigational_format?
+        Devise.navigational_formats.include?(request_format)
+      end
+    end
+  end
+end
\ No newline at end of file
diff --git a/lib/devise/failure_app.rb b/lib/devise/failure_app.rb
index e69c5a47..578fcecc 100644
--- a/lib/devise/failure_app.rb
+++ b/lib/devise/failure_app.rb
@@ -10,6 +10,7 @@ module Devise
     include ActionController::UrlFor
     include ActionController::Redirecting
     include Rails.application.routes.url_helpers
+    include Devise::Controllers::SharedHelpers
 
     delegate :flash, :to => :request
 
@@ -83,7 +84,7 @@ module Devise
       if request.xhr?
         Devise.http_authenticatable_on_xhr
       else
-        !(request_format && Devise.navigational_formats.include?(request_format))
+        !(request_format && is_navigational_format?)
       end
     end
 
@@ -135,9 +136,5 @@ module Devise
     def store_location!
       session["#{scope}_return_to"] = attempted_path if request.get? && !http_auth?
     end
-
-    def request_format
-      @request_format ||= Devise::Controllers::InternalHelpers.request_format(request)
-    end
   end
 end