diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index cd47d1f8336b94c4c17ac17b89e0e5002ecabfa1..f5ab1e2350012b56d200265c198810ee2fe7bcb3 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -204,7 +204,7 @@ def to_a #:nodoc:
     self.middleware_stack = ActionController::MiddlewareStack.new
 
     def self.inherited(base) # :nodoc:
-      base.middleware_stack = self.middleware_stack.dup
+      base.middleware_stack = middleware_stack.dup
       super
     end