diff --git a/htdocs/emailcollector/class/emailcollector.class.php b/htdocs/emailcollector/class/emailcollector.class.php
index 1f30afa96c5..27e9d867b96 100644
--- a/htdocs/emailcollector/class/emailcollector.class.php
+++ b/htdocs/emailcollector/class/emailcollector.class.php
@@ -2258,7 +2258,7 @@ class EmailCollector extends CommonObject
 									$trackid = $objectemail->track_id;
 								}
 								if (empty($objectemail->origin_references)) {
-									$objectemail->origin_references = $headers['References'];
+									$objectemail->origin_references = !empty($headers['References']) ? $headers['References'] : null;
 									$changeonticket_references = true;
 								} else {
 									foreach ($arrayofreferences as $key => $referencetmp) {