diff --git a/actionpack/lib/action_dispatch/middleware/stack.rb b/actionpack/lib/action_dispatch/middleware/stack.rb
index 5a029a60d1..6f243574e4 100644
--- a/actionpack/lib/action_dispatch/middleware/stack.rb
+++ b/actionpack/lib/action_dispatch/middleware/stack.rb
@@ -1,4 +1,5 @@
 require "active_support/inflector/methods"
+require "active_support/dependencies"
 
 module ActionDispatch
   class MiddlewareStack < Array