diff --git a/src/activity-vocabulary.lisp b/src/activity-vocabulary.lisp
index 20c3176..dd4a354 100644
--- a/src/activity-vocabulary.lisp
+++ b/src/activity-vocabulary.lisp
@@ -149,3 +149,10 @@ of NAME."
 ;; https://www.w3.org/ns/activitystreams#Tombstone
 (defclass-w-accessors tombstone (object)
   (former-type deleted))
+
+
+
+;;; Extended Link types
+;;; ————————————————————————————————————————
+(defclass-empty-children link
+  (mention))