diff --git a/app/models/related_content_score.rb b/app/models/related_content_score.rb
index 6be6a0388..73248ecce 100644
--- a/app/models/related_content_score.rb
+++ b/app/models/related_content_score.rb
@@ -1,6 +1,8 @@
 class RelatedContentScore < ActiveRecord::Base
   belongs_to :related_content, touch: true, counter_cache: :related_content_scores_count
+  belongs_to :user
 
-  validates :user_id, presence: true
-  validates :related_content_id, presence: true
+  validates :user, presence: true
+  validates :related_content, presence: true
+  validates :related_content_id, uniqueness: { scope: [:user_id] }
 end