diff --git a/db/migrate/20170609115401_add_extension_to_topic_links.rb b/db/migrate/20170609115401_add_extension_to_topic_links.rb
index 8360b0ef08..fbe8b9c184 100644
--- a/db/migrate/20170609115401_add_extension_to_topic_links.rb
+++ b/db/migrate/20170609115401_add_extension_to_topic_links.rb
@@ -1,5 +1,6 @@
 class AddExtensionToTopicLinks < ActiveRecord::Migration
   def change
     add_column :topic_links, :extension, :string, limit: 5
+    add_index :topic_links, :extension
   end
 end