diff --git a/src/IntesaSanPaoloClient.php b/src/IntesaSanPaoloClient.php
index ee84cc8..6952880 100644
--- a/src/IntesaSanPaoloClient.php
+++ b/src/IntesaSanPaoloClient.php
@@ -387,6 +387,10 @@ public function createInstantPayment( PaymentExecution $payment ): PaymentExecut
 			$data['resubmitId'] = $payment->getResubmitId();
 		}
 		
+		if( is_null( $data['siaCode'] ) ) {
+			$data['siaCode'] = '';
+		}
+		
 		$paymentExecutedResponse = $this->request( 'POST', sprintf( '%s/payments/sct/instant', $this->getApiBaseUri() ), [], $data );
 		
 		return new PaymentExecuted( $paymentExecutedResponse );
diff --git a/src/Models/PaymentSimulated.php b/src/Models/PaymentSimulated.php
index aa7bee1..2dc1545 100755
--- a/src/Models/PaymentSimulated.php
+++ b/src/Models/PaymentSimulated.php
@@ -6,12 +6,11 @@
 
 class PaymentSimulated extends GenericPaymentResult {
 	/**
+	 * [ ACCP accepted, RJCT rejected ]
 	 * @var string
 	 */
 	private $ValidationStatus;
 	
-	
-	
 	/**
 	 * Hydrates specific data
 	 * @param stdClass $data
@@ -24,7 +23,6 @@ protected function hydrateData( stdClass $data ) {
 		$this->ValidationStatus = $payload->validationStatus;
 	}
 	
-	
 	/**
 	 * @return string|null
 	 */