diff --git a/lib/activityobject.php b/lib/activityobject.php
index c506b17e85..fc47485c18 100644
--- a/lib/activityobject.php
+++ b/lib/activityobject.php
@@ -32,6 +32,8 @@ if (!defined('STATUSNET')) {
     exit(1);
 }
 
+require_once(INSTALLDIR.'/lib/activitystreamjsondocument.php');
+
 /**
  * A noun-ish thing in the activity universe
  *