diff --git a/typo3/sysext/core/Classes/Authentication/AbstractUserAuthentication.php b/typo3/sysext/core/Classes/Authentication/AbstractUserAuthentication.php
index fc8419fd8406b943db01a2547b65a2a8c342c3cd..d1c4c9379e2b59cd5e30ddd034de90d76748d90c 100644
--- a/typo3/sysext/core/Classes/Authentication/AbstractUserAuthentication.php
+++ b/typo3/sysext/core/Classes/Authentication/AbstractUserAuthentication.php
@@ -212,7 +212,7 @@ abstract class AbstractUserAuthentication implements LoggerAwareInterface
      *
      * @var Cookie|null
      */
-    protected ?Cookie $setCookie;
+    protected ?Cookie $setCookie = null;
 
     /**
      * Initialize some important variables
@@ -285,7 +285,7 @@ abstract class AbstractUserAuthentication implements LoggerAwareInterface
      */
     public function appendCookieToResponse(ResponseInterface $response): ResponseInterface
     {
-        if (isset($this->setCookie)) {
+        if ($this->setCookie !== null) {
             $response = $response->withAddedHeader('Set-Cookie', $this->setCookie->__toString());
         }
         return $response;