diff --git a/plugin.rb b/plugin.rb
index c5a7730..29d0afb 100644
--- a/plugin.rb
+++ b/plugin.rb
@@ -366,6 +366,7 @@ SQL
   end
 
   require_dependency 'topic_list_item_serializer'
+  require_dependency 'listable_topic_serializer'
 
   class ::TopicListItemSerializer
     attributes :has_accepted_answer, :can_have_answer