just add the writer rather than adding both and removing one

actionpack/lib/action_dispatch/routing/url_for.rb

@@ -90,8 +90,7 @@ module UrlFor
           if respond_to?(:class_attribute)
             class_attribute :default_url_options
           else
-            mattr_accessor :default_url_options
-            remove_method :default_url_options
+            mattr_writer :default_url_options
           end
 
           self.default_url_options = {}