1 files changed, 16 insertions, 3 deletions
diff --git a/railties/lib/rails/configuration.rb b/railties/lib/rails/configuration.rb
index d99d27a756..30eafd59f2 100644
--- a/railties/lib/rails/configuration.rb
+++ b/railties/lib/rails/configuration.rb
@@ -33,9 +33,9 @@ module Rails
     #     config.middleware.delete ActionDispatch::Flash
     #
     class MiddlewareStackProxy
-      def initialize
-        @operations = []
-        @delete_operations = []
+      def initialize(operations = [], delete_operations = [])
+        @operations = operations
+        @delete_operations = delete_operations
       end
 
       def insert_before(*args, &block)
@@ -71,6 +71,19 @@ module Rails
 
         other
       end
+
+      def +(other) # :nodoc:
+        MiddlewareStackProxy.new(@operations + other.operations, @delete_operations + other.delete_operations)
+      end
+
+      protected
+        def operations
+          @operations
+        end
+
+        def delete_operations
+          @delete_operations
+        end
     end
 
     class Generators #:nodoc: