1 files changed, 10 insertions, 1 deletions
diff --git a/railties/lib/rails/engine.rb b/railties/lib/rails/engine.rb
index c0607950b5..409502cb08 100644
--- a/railties/lib/rails/engine.rb
+++ b/railties/lib/rails/engine.rb
@@ -152,13 +152,22 @@ module Rails
     end
 
     def app
-      @app ||= config.middleware.build(endpoint)
+      @app ||= begin
+        config.middleware = config.middleware.merge_into(default_middleware_stack)
+        config.middleware.build(endpoint)
+      end
     end
 
     def endpoint
       self.class.endpoint || routes
     end
 
+    def default_middleware_stack
+      ActionDispatch::MiddlewareStack.new.tap do |middleware|
+        middleware.use ::ActionDispatch::Static, paths.public.to_a.first if config.serve_static_assets
+      end
+    end
+
     def call(env)
       app.call(env)
     end