diff --git a/include/feedutils.php b/include/feedutils.php
index c9c7522b1..02decca69 100644
--- a/include/feedutils.php
+++ b/include/feedutils.php
@@ -1505,7 +1505,7 @@ function atom_entry($item, $type, $author, $owner, $comment = false, $cid = 0, $
 
 	if(($item['parent'] != $item['id']) || ($item['parent_mid'] !== $item['mid']) || (($item['thr_parent'] !== '') && ($item['thr_parent'] !== $item['mid']))) {
 		$parent_item = (($item['thr_parent']) ? $item['thr_parent'] : $item['parent_mid']);
-		$o .= '<thr:in-reply-to ref="' . 'X-ZOT:' . xmlify($parent_item) . '" type="text/html" href="' .  xmlify($item['plink']) . '" />' . "\r\n";
+		$o .= '<thr:in-reply-to ref="' . xmlify($parent_item) . '" type="text/html" href="' .  xmlify($item['plink']) . '" />' . "\r\n";
 	}
 
 	if(activity_match($item['obj_type'],ACTIVITY_OBJ_EVENT) && activity_match($item['verb'],ACTIVITY_POST)) {