diff --git a/src/model/NotificationPayload.php b/src/model/NotificationPayload.php
index 0c382b5..74f44f8 100644
--- a/src/model/NotificationPayload.php
+++ b/src/model/NotificationPayload.php
@@ -30,32 +30,32 @@ class NotificationPayload
 
     public static function createFromArray($notification) {
         $instance = new self();
-        $instance->environment = $notification('environment');
-        $instance->password = $notification('password');
-        $instance->notificationType = $notification('notification_type');
-        $instance->cancellationDate = $notification('cancellation_date');
-        $instance->cancellationDatePst = $notification('cancellation_date_pst');
-        $instance->cancellationDateMs = $notification('cancellation_date_ms');
-        $instance->webOrderLineItemId = $notification('web_order_line_item_id');
-        $instance->latestReceipt = $notification('latest_receipt');
+        $instance->environment = $notification['environment'];
+        $instance->password = $notification['password'];
+        $instance->notificationType = $notification['notification_type'];
+        $instance->cancellationDate = $notification['cancellation_date'] ?? null;
+        $instance->cancellationDatePst = $notification['cancellation_date_pst'] ?? null;
+        $instance->cancellationDateMs = $notification['cancellation_date_ms'] ?? null;
+        $instance->webOrderLineItemId = $notification['web_order_line_item_id'] ?? null;
+        $instance->latestReceipt = $notification['latest_receipt'] ?? null;
         if (isset($notification['latest_receipt_info'])) {
-            $instance->latestReceiptInfo = Receipt::createFromArray($notification('latest_receipt_info'));
+            $instance->latestReceiptInfo = Receipt::createFromArray($notification['latest_receipt_info']);
         } else {
             $instance->latestReceiptInfo = null;
         }
-        $instance->latestExpiredReceipt = $notification('latest_expired_receipt');
+        $instance->latestExpiredReceipt = $notification['latest_expired_receipt'] ?? null;
         if (isset($notification['latest_expired_receipt_info'])) {
-            $instance->latestExpiredReceiptInfo = Receipt::createFromArray($notification('latest_expired_receipt_info'));
+            $instance->latestExpiredReceiptInfo = Receipt::createFromArray($notification['latest_expired_receipt_info']);
         } else {
             $instance->latestExpiredReceiptInfo = null;
         }
-        $instance->autoRenewStatus = $notification('auto_renew_status');
-        $instance->autoRenewProductId = $notification('auto_renew_product_id');
-        $instance->autoRenewStatusChangeDate = $notification('auto_renew_status_change_date');
-        $instance->autoRenewStatusChangeDatePst = $notification('auto_renew_status_change_date_pst');
-        $instance->autoRenewStatusChangeDateMs = $notification('auto_renew_status_change_date_ms');
+        $instance->autoRenewStatus = $notification['auto_renew_status'];
+        $instance->autoRenewProductId = $notification['auto_renew_product_id'];
+        $instance->autoRenewStatusChangeDate = $notification['auto_renew_status_change_date'] ?? null;
+        $instance->autoRenewStatusChangeDatePst = $notification['auto_renew_status_change_date_pst'] ?? null;
+        $instance->autoRenewStatusChangeDateMs = $notification['auto_renew_status_change_date_ms'] ?? null;
         if (isset($notification['pending_renewal_info'])) {
-            foreach ($notification('pending_renewal_info') as $pendingRenewalInfo) {
+            foreach ($notification['pending_renewal_info'] as $pendingRenewalInfo) {
                 $instance->pendingRenewalInfo[] = RenewalInfo::createFromRequest($pendingRenewalInfo);
             }
         } else {