diff --git a/lib/action_controller/serialization.rb b/lib/action_controller/serialization.rb
index 9c537218..0e1d8fff 100644
--- a/lib/action_controller/serialization.rb
+++ b/lib/action_controller/serialization.rb
@@ -80,13 +80,14 @@ module ActionController
 
     def build_json_serializer(resource, options = {})
       options = default_serializer_options.merge(options)
+      @namespace_for_serializer = options.fetch(:namespace, nil)
 
       if serializer = options.fetch(:serializer, default_serializer(resource))
         options[:scope] = serialization_scope unless options.has_key?(:scope)
 
         if resource.respond_to?(:to_ary)
-          options[:resource_name] ||= controller_name 
-          options[:namespace] ||= namespace_for_serializer if namespace_for_serializer
+          options[:resource_name]= controller_name 
+          options[:namespace] = namespace_for_serializer if namespace_for_serializer
         end
 
         serializer.new(resource, options)