1 files changed, 6 insertions, 1 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/stack.rb b/actionpack/lib/action_dispatch/middleware/stack.rb
index 28e8fbdab8..bbf734f103 100644
--- a/actionpack/lib/action_dispatch/middleware/stack.rb
+++ b/actionpack/lib/action_dispatch/middleware/stack.rb
@@ -75,6 +75,11 @@ module ActionDispatch
       middlewares[i]
     end
 
+    def unshift(*args, &block)
+      middleware = self.class::Middleware.new(*args, &block)
+      middlewares.unshift(middleware)
+    end
+
     def initialize_copy(other)
       self.middlewares = other.middlewares.dup
     end
@@ -110,7 +115,7 @@ module ActionDispatch
     def build(app = nil, &block)
       app ||= block
       raise "MiddlewareStack#build requires an app" unless app
-      middlewares.reverse.inject(app) { |a, e| e.build(a) }
+      middlewares.freeze.reverse.inject(app) { |a, e| e.build(a) }
     end
 
   protected