diff --git a/vendor/plugins/user_stamp/lib/user_stamp.rb b/vendor/plugins/user_stamp/lib/user_stamp.rb
index 647e045..001ad07 100644
--- a/vendor/plugins/user_stamp/lib/user_stamp.rb
+++ b/vendor/plugins/user_stamp/lib/user_stamp.rb
@@ -13,7 +13,7 @@ module UserStamp
   
   module ClassMethods
     def user_stamp(*models)
-      models.each { |klass| klass.add_observer(UserStampSweeper.instance) }
+      models.each { |klass| UserStampSweeper.observe(klass) }
       
       class_eval do
         cache_sweeper :user_stamp_sweeper
--
libgit2 0.21.2