diff --git a/app/code/LiqpayMagento/LiqPay/Helper/Data.php b/app/code/LiqpayMagento/LiqPay/Helper/Data.php
index cf89f02..289d8a2 100644
--- a/app/code/LiqpayMagento/LiqPay/Helper/Data.php
+++ b/app/code/LiqpayMagento/LiqPay/Helper/Data.php
@@ -95,7 +95,7 @@ public function getTestOrderSurfix()
         ));
     }
 
-    public function getLiqPayDescription(\Magento\Sales\Api\Data\OrderInterface $order = null)
+    public function getLiqPayDescription(?\Magento\Sales\Api\Data\OrderInterface $order = null)
     {
         $description = trim($this->scopeConfig->getValue(
             self::XML_PATH_DESCRIPTION,
diff --git a/app/code/LiqpayMagento/LiqPay/Model/Payment.php b/app/code/LiqpayMagento/LiqPay/Model/Payment.php
index e858e84..2c89eb1 100644
--- a/app/code/LiqpayMagento/LiqPay/Model/Payment.php
+++ b/app/code/LiqpayMagento/LiqPay/Model/Payment.php
@@ -93,7 +93,7 @@ public function capture(\Magento\Payment\Model\InfoInterface $payment, $amount)
         }
     }
 
-    public function isAvailable(\Magento\Quote\Api\Data\CartInterface $quote = null)
+    public function isAvailable(?\Magento\Quote\Api\Data\CartInterface $quote = null)
     {
         if (!$this->_liqPay->getHelper()->isEnabled()) {
             return false;
@@ -104,4 +104,4 @@ public function isAvailable(\Magento\Quote\Api\Data\CartInterface $quote = null)
         }
         return parent::isAvailable($quote);
     }
-}
\ No newline at end of file
+}