diff --git a/Security/Authenticator/RefreshTokenAuthenticator.php b/Security/Authenticator/RefreshTokenAuthenticator.php
index fa9e128e..eeb6bf2f 100644
--- a/Security/Authenticator/RefreshTokenAuthenticator.php
+++ b/Security/Authenticator/RefreshTokenAuthenticator.php
@@ -146,7 +146,7 @@ public function onAuthenticationFailure(Request $request, AuthenticationExceptio
     /**
      * @return Response
      */
-    public function start(Request $request, AuthenticationException $authException = null)
+    public function start(Request $request, ?AuthenticationException $authException = null)
     {
         $data = [
             // you might translate this message
diff --git a/Security/Http/Authenticator/RefreshTokenAuthenticator.php b/Security/Http/Authenticator/RefreshTokenAuthenticator.php
index 6102ff71..6d69de51 100644
--- a/Security/Http/Authenticator/RefreshTokenAuthenticator.php
+++ b/Security/Http/Authenticator/RefreshTokenAuthenticator.php
@@ -178,7 +178,7 @@ public function onAuthenticationFailure(Request $request, AuthenticationExceptio
         return $this->failureHandler->onAuthenticationFailure($request, $exception);
     }
 
-    public function start(Request $request, AuthenticationException $authException = null): Response
+    public function start(Request $request, ?AuthenticationException $authException = null): Response
     {
         $event = new RefreshTokenNotFoundEvent(
             new MissingTokenException('JWT Refresh Token not found', 0, $authException),