diff --git a/lib/memoist.rb b/lib/memoist.rb
index 54b67e6..7f9fb6a 100644
--- a/lib/memoist.rb
+++ b/lib/memoist.rb
@@ -132,7 +132,7 @@ def memoize(*method_names)
         include InstanceMethods
 
         if method_defined?(unmemoized_method)
-          warn "Already memoized #{method_name}"
+          warn "[#{self}] Already memoized #{method_name}"
           return
         end
         alias_method unmemoized_method, method_name