diff --git a/internal-api/dao/calendar_dao.php b/internal-api/dao/calendar_dao.php
index 16727735..3c30f839 100644
--- a/internal-api/dao/calendar_dao.php
+++ b/internal-api/dao/calendar_dao.php
@@ -137,7 +137,7 @@ function update_ticket_due_date($ticket, $hesk_settings) {
     if ($ticket['due_date'] != NULL) {
         $due_date = "'" . date('Y-m-d H:i:s', strtotime($ticket['due_date'])) . "'";
     }
-    $sql = "UPDATE `" . hesk_dbEscape($hesk_settings['db_pfix']) . "tickets` SET `due_date` = {$due_date}
+    $sql = "UPDATE `" . hesk_dbEscape($hesk_settings['db_pfix']) . "tickets` SET `due_date` = {$due_date}, `overdue_email_sent` = '0'
         WHERE `trackid` = '" . hesk_dbEscape($ticket['trackid']) . "'";
 
     hesk_dbQuery($sql);