diff --git a/app/models/photo_flag.rb b/app/models/photo_flag.rb
index bbfa518..ae96a9d 100644
--- a/app/models/photo_flag.rb
+++ b/app/models/photo_flag.rb
@@ -1,5 +1,5 @@
 class PhotoFlag < ActiveRecord::Base
   belongs_to :photo, :counter_cache => true
   belongs_to :user
-  validates_uniqueness_of :user_id
+  validates_uniqueness_of :user_id, :scope => :photo_id
 end