diff --git a/lib/data_mapper/mapper/attribute_set.rb b/lib/data_mapper/mapper/attribute_set.rb
index <HASH>..<HASH> 100644
--- a/lib/data_mapper/mapper/attribute_set.rb
+++ b/lib/data_mapper/mapper/attribute_set.rb
@@ -90,7 +90,9 @@ module DataMapper
           end
         end
 
-        each { |attribute| instance << attribute.clone unless instance[attribute.name] }
+        each do |attribute|
+          instance << attribute.clone unless instance[attribute.name]
+        end
 
         instance
       end
Use do/end blocks for #each in AttributeSet#merge