diff --git a/src/Auth/LoginAttemptInfo.php b/src/Auth/LoginAttemptInfo.php
index 025c11c..9c3abeb 100644
--- a/src/Auth/LoginAttemptInfo.php
+++ b/src/Auth/LoginAttemptInfo.php
@@ -29,7 +29,7 @@ class LoginAttemptInfo {
         return $this->userId !== null;
     }
 
-    public function getUserId(): string {
+    public function getUserId(): ?string {
         return $this->userId;
     }