diff --git src/bp-groups/bp-groups-notifications.php src/bp-groups/bp-groups-notifications.php
index 3bd75d7..5073bb7 100644
--- src/bp-groups/bp-groups-notifications.php
+++ src/bp-groups/bp-groups-notifications.php
@@ -1178,8 +1178,9 @@ function groups_format_notifications( $action, $item_id, $secondary_item_id, $to
 	 * @param int    $item_id           The primary item ID.
 	 * @param int    $secondary_item_id The secondary item ID.
 	 * @param int    $total_items       Total amount of items to format.
+	 * @param string $format            Format returned items as a string or array.
 	 */
-	do_action( 'groups_format_notifications', $action, $item_id, $secondary_item_id, $total_items );
+	do_action( 'groups_format_notifications', $action, $item_id, $secondary_item_id, $total_items, $format );
 
 	return false;
 }