diff --git a/src/services/Vouchers.php b/src/services/Vouchers.php
index 7d80f1a..6d445b7 100755
--- a/src/services/Vouchers.php
+++ b/src/services/Vouchers.php
@@ -36,7 +36,7 @@ public function getVoucherById(int $id, $siteId = null): ?Voucher
 
     public function afterSaveSiteHandler(SiteEvent $event): void
     {
-        if ($event->isNew) {
+        if ($event->isNew && isset($event->oldPrimarySiteId)) {
             $oldPrimarySiteId = $event->oldPrimarySiteId;
 
             $elementTypes = [