diff --git a/actionmailer/lib/action_mailer/railtie.rb b/actionmailer/lib/action_mailer/railtie.rb
index a2b00addc9c9026523dfbec22c59b39e24eb69fc..889ae344077191560420da4bf612a0cb930c0a22 100644
--- a/actionmailer/lib/action_mailer/railtie.rb
+++ b/actionmailer/lib/action_mailer/railtie.rb
@@ -21,7 +21,7 @@ class Railtie < Rails::Railtie
       ActiveSupport.on_load(:action_mailer) do
         include AbstractController::UrlFor
         extend ::AbstractController::Railties::RoutesHelpers.with(app.routes)
-        include app.routes.mounted_helpers(:app)
+        include app.routes.mounted_helpers
         options.each { |k,v| send("#{k}=", v) }
       end
     end
diff --git a/actionpack/lib/action_controller/railtie.rb b/actionpack/lib/action_controller/railtie.rb
index d26b7e2486473500ee96786bfd095d04ffd5d243..aea28d926588ddc9732ba621d7687896943e5097 100644
--- a/actionpack/lib/action_controller/railtie.rb
+++ b/actionpack/lib/action_controller/railtie.rb
@@ -27,7 +27,7 @@ class Railtie < Rails::Railtie
       options.page_cache_directory ||= paths.public.to_a.first
 
       ActiveSupport.on_load(:action_controller) do
-        include app.routes.mounted_helpers(:app)
+        include app.routes.mounted_helpers
         extend ::AbstractController::Railties::RoutesHelpers.with(app.routes)
         extend ::ActionController::Railties::Paths.with(app)
         options.each { |k,v| send("#{k}=", v) }
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 956bd2e719365d9b399895230a877fb7e9ea8a49..835ba03784d1303602b8afab4fb38534af3aa114 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -262,7 +262,7 @@ def install_helpers(destinations = [ActionController::Base, ActionView::Base], r
       module MountedHelpers
       end
 
-      def mounted_helpers(name = nil)
+      def mounted_helpers(name = :main_app)
         define_mounted_helper(name) if name
         MountedHelpers
       end
diff --git a/actionpack/test/dispatch/prefix_generation_test.rb b/actionpack/test/dispatch/prefix_generation_test.rb
index 3b47a1b72d7258a81bd77590546a50a6f6459624..26d76557dd097d8b113dcc695f42d488098fb72a 100644
--- a/actionpack/test/dispatch/prefix_generation_test.rb
+++ b/actionpack/test/dispatch/prefix_generation_test.rb
@@ -72,7 +72,7 @@ def klass.name; self end
 
     class ::InsideEngineGeneratingController < ActionController::Base
       include BlogEngine.routes.url_helpers
-      include RailsApplication.routes.mounted_helpers(:app)
+      include RailsApplication.routes.mounted_helpers
 
       def index
         render :text => posts_path
@@ -83,9 +83,9 @@ def show
       end
 
       def url_to_application
-        path = app.url_for( :controller => "outside_engine_generating",
-                            :action => "index",
-                            :only_path => true)
+        path = main_app.url_for(:controller => "outside_engine_generating",
+                                :action => "index",
+                                :only_path => true)
         render :text => path
       end
 
diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index 477bbbc1e7a7cb96856cbd6240a32e238bfd6c6f..f9f06299a0301cdbc2ddb95e1ba77d922f48fc5f 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -23,6 +23,7 @@ def initialize(*)
         @session_options = {}
         @time_zone = "UTC"
         @middleware = app_middleware
+        @asset_path = '/'
       end
 
       def asset_path=(value)
diff --git a/railties/test/application/initializers/frameworks_test.rb b/railties/test/application/initializers/frameworks_test.rb
index 61340e82c3b40dfd2d36fe56b637b1ee115fa227..6970ea7b7acc6daad67024375f94e92058c31d8f 100644
--- a/railties/test/application/initializers/frameworks_test.rb
+++ b/railties/test/application/initializers/frameworks_test.rb
@@ -61,7 +61,7 @@ def notify
 
       require "#{app_path}/config/environment"
       assert Foo.method_defined?(:foo_path)
-      assert Foo.method_defined?(:app)
+      assert Foo.method_defined?(:main_app)
       assert_equal ["notify"], Foo.action_methods
     end
 
diff --git a/railties/test/application/routing_test.rb b/railties/test/application/routing_test.rb
index d0c6cb51ca0d42e17b3d66fbeaf4879b5ab37045..b4ff14409f8b1608d006a4d5877ec52379b2fe4d 100644
--- a/railties/test/application/routing_test.rb
+++ b/railties/test/application/routing_test.rb
@@ -203,7 +203,7 @@ def baz
         assert_equal 'bar', last_response.body
 
         app_file 'config/routes.rb', <<-RUBY
-          AppTemplate::Application.routes.draw do |map|
+          AppTemplate::Application.routes.draw do
             match 'foo', :to => 'foo#baz'
           end
         RUBY
diff --git a/railties/test/railties/engine_test.rb b/railties/test/railties/engine_test.rb
index fabd561bd2c6f51a05abd519e993d285f0f69f74..6fc166e054729f86b61dca9f632c4f6d8f7bdae8 100644
--- a/railties/test/railties/engine_test.rb
+++ b/railties/test/railties/engine_test.rb
@@ -281,6 +281,34 @@ def index
       assert_equal expected, stripped_body
     end
 
+    test "default application's asset_path" do
+      @plugin.write "config/routes.rb", <<-RUBY
+        Bukkits::Engine.routes.draw do
+          match "/foo" => "foo#index"
+        end
+      RUBY
+
+      @plugin.write "app/controllers/foo_controller.rb", <<-RUBY
+        class FooController < ActionController::Base
+          def index
+          end
+        end
+      RUBY
+
+      @plugin.write "app/views/foo/index.html.erb", <<-RUBY
+        <%= compute_public_path("/foo", "") %>
+      RUBY
+
+      boot_rails
+
+      env = Rack::MockRequest.env_for("/foo")
+      response = Bukkits::Engine.call(env)
+      stripped_body = response[2].body.strip
+
+      expected =  "/bukkits/foo"
+      assert_equal expected, stripped_body
+    end
+
     test "engine's files are served via ActionDispatch::Static" do
       add_to_config "config.serve_static_assets = true"
 
@@ -437,7 +465,7 @@ def from_app
           end
 
           def routes_helpers_in_view
-            render :inline => "<%= foo_path %>, <%= app.bar_path %>"
+            render :inline => "<%= foo_path %>, <%= main_app.bar_path %>"
           end
 
           def polymorphic_path_without_namespace
diff --git a/railties/test/railties/mounted_engine_test.rb b/railties/test/railties/mounted_engine_test.rb
index 73b7e5b2e02424550d3cf9263ab5c3b00075ebe8..b52ced92ec2f4214b142f3cc668655e4b0196328 100644
--- a/railties/test/railties/mounted_engine_test.rb
+++ b/railties/test/railties/mounted_engine_test.rb
@@ -70,14 +70,14 @@ def index
             end
 
             def generate_application_route
-              path = app.url_for(:controller => "/main",
+              path = main_app.url_for(:controller => "/main",
                                  :action => "index",
                                  :only_path => true)
               render :text => path
             end
 
             def application_route_in_view
-              render :inline => "<%= app.root_path %>"
+              render :inline => "<%= main_app.root_path %>"
             end
           end
         end