diff --git a/calendar/inc/class.calendar_owner_etemplate_widget.inc.php b/calendar/inc/class.calendar_owner_etemplate_widget.inc.php
index 8514d53c3a..fa89ce4beb 100644
--- a/calendar/inc/class.calendar_owner_etemplate_widget.inc.php
+++ b/calendar/inc/class.calendar_owner_etemplate_widget.inc.php
@@ -57,7 +57,7 @@ class calendar_owner_etemplate_widget extends Etemplate\Widget\Taglist
 		}
 
 		// Add external owners that a select account widget will not find
-		foreach($value as &$owner)
+		foreach((array)$value as $owner)
 		{
 			$label = self::get_owner_label($owner);
 			$info = array();