diff --git a/app/models/user_identity.rb b/app/models/user_identity.rb
index c5a7c08f6..e0ae551e4 100644
--- a/app/models/user_identity.rb
+++ b/app/models/user_identity.rb
@@ -1,4 +1,5 @@
 class UserIdentity < ActiveRecord::Base
   belongs_to :user
   validates :provider, uniqueness: { scope: :user_id }
+  validates :uid, uniqueness: { scope: :provider }
 end