uniqueness_validator.diff

diff --git a/dm-validations/lib/dm-validations/validators/uniqueness_validator.rb b/dm-validations/lib/dm-validations/validators/uniquen
index 16fc786..6bec021 100644
--- a/dm-validations/lib/dm-validations/validators/uniqueness_validator.rb
+++ b/dm-validations/lib/dm-validations/validators/uniqueness_validator.rb
@@ -22,8 +22,11 @@ module DataMapper
 
         repository_name = target.repository.name
 
+        fields  = target.model.key.dup
+        fields << target.model.properties[field_name]
+
         opts = {
-          :fields    => target.model.key,
+          :fields    => fields,
           field_name => target.validation_property_value(field_name),
         }