diff --git a/boot.php b/boot.php
index 7cc158a26..e75b2abd9 100644
--- a/boot.php
+++ b/boot.php
@@ -204,6 +204,7 @@ define('NAMESPACE_ZOT',             'http://purl.org/zot');
 define('NAMESPACE_DFRN',            'http://purl.org/macgirvin/dfrn/1.0');
 define('NAMESPACE_THREAD',          'http://purl.org/syndication/thread/1.0');
 define('NAMESPACE_TOMB',            'http://purl.org/atompub/tombstones/1.0');
+define('NAMESPACE_ACTIVITY2',       'https://www.w3.org/ns/activitystreams#');
 define('NAMESPACE_ACTIVITY',        'http://activitystrea.ms/spec/1.0/');
 define('NAMESPACE_ACTIVITY_SCHEMA', 'http://activitystrea.ms/schema/1.0/');
 define('NAMESPACE_MEDIA',           'http://purl.org/syndication/atommedia');
@@ -246,6 +247,7 @@ define('ACTIVITY_FAVORITE',    NAMESPACE_ACTIVITY_SCHEMA . 'favorite');
 define('ACTIVITY_UNFAVORITE',  NAMESPACE_ACTIVITY_SCHEMA . 'unfavorite');
 define('ACTIVITY_SHARE',       NAMESPACE_ACTIVITY_SCHEMA . 'share');
 define('ACTIVITY_DELETE',      NAMESPACE_ACTIVITY_SCHEMA . 'delete');
+define('ACTIVITY2_ANNOUNCE',   NAMESPACE_ACTIVITY2       . 'Announce');
 
 define('ACTIVITY_POKE',        NAMESPACE_ZOT . '/activity/poke');
 
diff --git a/include/conversation.php b/include/conversation.php
index 9f4313a39..f7e08571c 100644
--- a/include/conversation.php
+++ b/include/conversation.php
@@ -396,7 +396,7 @@ function visible_activity($item) {
 	 * likes (etc.) can apply to other things besides posts. Check if they are post children,
 	 * in which case we handle them specially
 	 */
-	$hidden_activities = [ACTIVITY_LIKE, ACTIVITY_DISLIKE, ACTIVITY_ATTEND, ACTIVITY_ATTENDNO, ACTIVITY_ATTENDMAYBE, ACTIVITY_FOLLOW];
+	$hidden_activities = [ACTIVITY_LIKE, ACTIVITY_DISLIKE, ACTIVITY_ATTEND, ACTIVITY_ATTENDNO, ACTIVITY_ATTENDMAYBE, ACTIVITY_FOLLOW, ACTIVITY2_ANNOUNCE];
 	foreach ($hidden_activities as $act) {
 		if (activity_match($item['verb'], $act)) {
 			return false;
diff --git a/src/Model/Item.php b/src/Model/Item.php
index 68bbdfd8f..b372f67ca 100644
--- a/src/Model/Item.php
+++ b/src/Model/Item.php
@@ -92,7 +92,7 @@ class Item extends BaseObject
 
 	// Never reorder or remove entries from this list. Just add new ones at the end, if needed.
 	// The item-activity table only stores the index and needs this array to know the matching activity.
-	const ACTIVITIES = [ACTIVITY_LIKE, ACTIVITY_DISLIKE, ACTIVITY_ATTEND, ACTIVITY_ATTENDNO, ACTIVITY_ATTENDMAYBE, ACTIVITY_FOLLOW];
+	const ACTIVITIES = [ACTIVITY_LIKE, ACTIVITY_DISLIKE, ACTIVITY_ATTEND, ACTIVITY_ATTENDNO, ACTIVITY_ATTENDMAYBE, ACTIVITY_FOLLOW, ACTIVITY2_ANNOUNCE];
 
 	private static $legacy_mode = null;