diff --git a/src/Plugin/Commerce/PaymentGateway/AuthorizeNet.php b/src/Plugin/Commerce/PaymentGateway/AuthorizeNet.php
index 8aefecb..48948d3 100644
--- a/src/Plugin/Commerce/PaymentGateway/AuthorizeNet.php
+++ b/src/Plugin/Commerce/PaymentGateway/AuthorizeNet.php
@@ -379,7 +379,7 @@ class AuthorizeNet extends OnsitePaymentGatewayBase implements AuthorizeNetInter
     $payment_method = $payment->getPaymentMethod();
     $transaction_request->addPayment(new CreditCardDataType([
       'cardNumber' => $payment_method->card_number->value,
-      'expirationDate' => $payment_method->card_exp_month->value . $payment_method->card_exp_year->value,
+      'expirationDate' => str_pad($payment_method->card_exp_month->value, 2, '0', STR_PAD_LEFT) . str_pad($payment_method->card_exp_year->value, 2, '0', STR_PAD_LEFT),
     ]));
     $request->setTransactionRequest($transaction_request);
     $response = $request->execute();