1 files changed, 20 insertions, 5 deletions
diff --git a/actionpack/lib/action_controller/middleware_stack.rb b/actionpack/lib/action_controller/middleware_stack.rb
index 1864bed23a..a6597a6fec 100644
--- a/actionpack/lib/action_controller/middleware_stack.rb
+++ b/actionpack/lib/action_controller/middleware_stack.rb
@@ -4,7 +4,12 @@ module ActionController
       attr_reader :klass, :args, :block
 
       def initialize(klass, *args, &block)
-        @klass = klass.is_a?(Class) ? klass : klass.to_s.constantize
+        if klass.is_a?(Class)
+          @klass = klass
+        else
+          @klass = klass.to_s.constantize
+        end
+
         @args = args
         @block = block
       end
@@ -21,18 +26,28 @@ module ActionController
       end
 
       def inspect
-        str = @klass.to_s
-        @args.each { |arg| str += ", #{arg.inspect}" }
+        str = klass.to_s
+        args.each { |arg| str += ", #{arg.inspect}" }
         str
       end
 
       def build(app)
-        klass.new(app, *args, &block)
+        if block
+          klass.new(app, *args, &block)
+        else
+          klass.new(app, *args)
+        end
       end
     end
 
+    def initialize(*args, &block)
+      super(*args)
+      block.call(self) if block_given?
+    end
+
     def use(*args, &block)
-      push(Middleware.new(*args, &block))
+      middleware = Middleware.new(*args, &block)
+      push(middleware)
     end
 
     def build(app)