diff --git a/db/migrate/20150617080349_add_index_on_post_notifications.rb b/db/migrate/20150617080349_add_index_on_post_notifications.rb
new file mode 100644
index 000000000..a8cbccfdc
--- /dev/null
+++ b/db/migrate/20150617080349_add_index_on_post_notifications.rb
@@ -0,0 +1,5 @@
+class AddIndexOnPostNotifications < ActiveRecord::Migration
+  def change
+    add_index :notifications, [:user_id, :topic_id, :post_number]
+  end
+end