diff --git a/UPGRADING.md b/UPGRADING.md
index 09f9ea5..5d94ece 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -14,7 +14,7 @@ Some major changes are:
 $redsysRequest = new RedsysRequest($redsysClient);
 $redsysRequest->createPaymentRequest(
     amount: 123.45,
-    orderNumber: '22013100005',
+    order: '22013100005',
     currency: Currency::EUR,
     transactionType: TransactionType::Autorizacion,
 );
@@ -24,7 +24,7 @@ $redsysRequest = RedsysRequest::create(
     $redsysClient,
     new RequestParameters(
         amountInCents: 123_45,
-        orderNumber: '22013100005',
+        order: '22013100005',
         currency: Currency::EUR,
         transactionType: TransactionType::Autorizacion,
         merchantUrl: 'https://example.com/redsysNotification',