diff --git a/app/code/Magento/Sales/Model/Service/CreditmemoService.php b/app/code/Magento/Sales/Model/Service/CreditmemoService.php
index c7541e6cb7e4859f1bc8b48b0f21d6dd8b0bde1b..24f56c0dbd595215956cd9134f4e8ca23ecf194c 100644
--- a/app/code/Magento/Sales/Model/Service/CreditmemoService.php
+++ b/app/code/Magento/Sales/Model/Service/CreditmemoService.php
@@ -195,7 +195,7 @@ class CreditmemoService implements \Magento\Sales\Api\CreditmemoManagementInterf
      */
     protected function validateForRefund(\Magento\Sales\Api\Data\CreditmemoInterface $creditmemo)
     {
-        if ($creditmemo->getId() && $creditmemo->getState() !== \Magento\Sales\Model\Order\Creditmemo::STATE_OPEN) {
+        if ($creditmemo->getId() && $creditmemo->getState() != \Magento\Sales\Model\Order\Creditmemo::STATE_OPEN) {
             throw new \Magento\Framework\Exception\LocalizedException(
                 __('We cannot register an existing credit memo.')
             );