diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index 8d68cc36d2..c3b5275665 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -52,11 +52,12 @@ module Rails
   #   11) Run config.after_initialize callbacks
   #
   class Application < Engine
-    autoload :Bootstrap,      'rails/application/bootstrap'
-    autoload :Configuration,  'rails/application/configuration'
-    autoload :Finisher,       'rails/application/finisher'
-    autoload :Railties,       'rails/engine/railties'
-    autoload :RoutesReloader, 'rails/application/routes_reloader'
+    autoload :Bootstrap,              'rails/application/bootstrap'
+    autoload :Configuration,          'rails/application/configuration'
+    autoload :DefaultMiddlewareStack, 'rails/application/default_middleware_stack'
+    autoload :Finisher,               'rails/application/finisher'
+    autoload :Railties,               'rails/engine/railties'
+    autoload :RoutesReloader,         'rails/application/routes_reloader'
 
     class << self
       def inherited(base)
@@ -102,7 +103,6 @@ def reload_routes!
       routes_reloader.reload!
     end
 
-
     # Return the application's KeyGenerator
     def key_generator
       # number of iterations selected based on consultation with the google security
@@ -275,96 +275,9 @@ def railties_initializers(current) #:nodoc:
       initializers
     end
 
-    def reload_dependencies? #:nodoc:
-      config.reload_classes_only_on_change != true || reloaders.map(&:updated?).any?
-    end
-
     def default_middleware_stack #:nodoc:
-      ActionDispatch::MiddlewareStack.new.tap do |middleware|
-        app = self
-
-        if rack_cache = load_rack_cache
-          require "action_dispatch/http/rack_cache"
-          middleware.use ::Rack::Cache, rack_cache
-        end
-
-        if config.force_ssl
-          middleware.use ::ActionDispatch::SSL, config.ssl_options
-        end
-
-        if config.action_dispatch.x_sendfile_header.present?
-          middleware.use ::Rack::Sendfile, config.action_dispatch.x_sendfile_header
-        end
-
-        if config.serve_static_assets
-          middleware.use ::ActionDispatch::Static, paths["public"].first, config.static_cache_control
-        end
-
-        middleware.use ::Rack::Lock unless allow_concurrency?
-        middleware.use ::Rack::Runtime
-        middleware.use ::Rack::MethodOverride
-        middleware.use ::ActionDispatch::RequestId
-
-        # Must come after Rack::MethodOverride to properly log overridden methods
-        middleware.use ::Rails::Rack::Logger, config.log_tags
-        middleware.use ::ActionDispatch::ShowExceptions, show_exceptions_app
-        middleware.use ::ActionDispatch::DebugExceptions, app
-        middleware.use ::ActionDispatch::RemoteIp, config.action_dispatch.ip_spoofing_check, config.action_dispatch.trusted_proxies
-
-        unless config.cache_classes
-          middleware.use ::ActionDispatch::Reloader, lambda { app.reload_dependencies? }
-        end
-
-        middleware.use ::ActionDispatch::Callbacks
-        middleware.use ::ActionDispatch::Cookies
-
-        if config.session_store
-          if config.force_ssl && !config.session_options.key?(:secure)
-            config.session_options[:secure] = true
-          end
-          middleware.use config.session_store, config.session_options
-          middleware.use ::ActionDispatch::Flash
-        end
-
-        middleware.use ::ActionDispatch::ParamsParser
-        middleware.use ::Rack::Head
-        middleware.use ::Rack::ConditionalGet
-        middleware.use ::Rack::ETag, "no-cache"
-      end
-    end
-
-    def allow_concurrency?
-      if config.allow_concurrency.nil?
-        config.cache_classes
-      else
-        config.allow_concurrency
-      end
-    end
-
-    def load_rack_cache
-      rack_cache = config.action_dispatch.rack_cache
-      return unless rack_cache
-
-      begin
-        require 'rack/cache'
-      rescue LoadError => error
-        error.message << ' Be sure to add rack-cache to your Gemfile'
-        raise
-      end
-
-      if rack_cache == true
-        {
-          metastore: "rails:/",
-          entitystore: "rails:/",
-          verbose: false
-        }
-      else
-        rack_cache
-      end
-    end
-
-    def show_exceptions_app
-      config.exceptions_app || ActionDispatch::PublicExceptions.new(Rails.public_path)
+      default_stack = DefaultMiddlewareStack.new(self, config, paths)
+      default_stack.build_stack
     end
 
     def build_original_fullpath(env) #:nodoc:
diff --git a/railties/lib/rails/application/default_middleware_stack.rb b/railties/lib/rails/application/default_middleware_stack.rb
new file mode 100644
index 0000000000..370c906086
--- /dev/null
+++ b/railties/lib/rails/application/default_middleware_stack.rb
@@ -0,0 +1,101 @@
+module Rails
+  class Application
+    class DefaultMiddlewareStack
+      attr_reader :config, :paths, :app
+
+      def initialize(app, config, paths)
+        @app = app
+        @config = config
+        @paths = paths
+      end
+
+      def build_stack
+        ActionDispatch::MiddlewareStack.new.tap do |middleware|
+          if rack_cache = load_rack_cache
+            require "action_dispatch/http/rack_cache"
+            middleware.use ::Rack::Cache, rack_cache
+          end
+
+          if config.force_ssl
+            middleware.use ::ActionDispatch::SSL, config.ssl_options
+          end
+
+          if config.action_dispatch.x_sendfile_header.present?
+            middleware.use ::Rack::Sendfile, config.action_dispatch.x_sendfile_header
+          end
+
+          if config.serve_static_assets
+            middleware.use ::ActionDispatch::Static, paths["public"].first, config.static_cache_control
+          end
+
+          middleware.use ::Rack::Lock unless allow_concurrency?
+          middleware.use ::Rack::Runtime
+          middleware.use ::Rack::MethodOverride
+          middleware.use ::ActionDispatch::RequestId
+
+          # Must come after Rack::MethodOverride to properly log overridden methods
+          middleware.use ::Rails::Rack::Logger, config.log_tags
+          middleware.use ::ActionDispatch::ShowExceptions, show_exceptions_app
+          middleware.use ::ActionDispatch::DebugExceptions, app
+          middleware.use ::ActionDispatch::RemoteIp, config.action_dispatch.ip_spoofing_check, config.action_dispatch.trusted_proxies
+
+          unless config.cache_classes
+            middleware.use ::ActionDispatch::Reloader, lambda { reload_dependencies? }
+          end
+
+          middleware.use ::ActionDispatch::Callbacks
+          middleware.use ::ActionDispatch::Cookies
+
+          if config.session_store
+            if config.force_ssl && !config.session_options.key?(:secure)
+              config.session_options[:secure] = true
+            end
+            middleware.use config.session_store, config.session_options
+            middleware.use ::ActionDispatch::Flash
+          end
+
+          middleware.use ::ActionDispatch::ParamsParser
+          middleware.use ::Rack::Head
+          middleware.use ::Rack::ConditionalGet
+          middleware.use ::Rack::ETag, "no-cache"
+        end
+      end
+
+      private
+
+        def reload_dependencies?
+          config.reload_classes_only_on_change != true || app.reloaders.map(&:updated?).any?
+        end
+
+        def allow_concurrency?
+          config.allow_concurrency.nil? ? config.cache_classes : config.allow_concurrency
+        end
+
+        def load_rack_cache
+          rack_cache = config.action_dispatch.rack_cache
+          return unless rack_cache
+
+          begin
+            require 'rack/cache'
+          rescue LoadError => error
+            error.message << ' Be sure to add rack-cache to your Gemfile'
+            raise
+          end
+
+          if rack_cache == true
+            {
+              metastore: "rails:/",
+              entitystore: "rails:/",
+              verbose: false
+            }
+          else
+            rack_cache
+          end
+        end
+
+        def show_exceptions_app
+          config.exceptions_app || ActionDispatch::PublicExceptions.new(Rails.public_path)
+        end
+    end
+  end
+end