diff --git a/lib/SimpleSAML/Utils/Auth.php b/lib/SimpleSAML/Utils/Auth.php
index 3b7ece04e14c972bc8c4d242eaa9fa56d02da1f6..285b87ec35720cb126093dfb898144164bb9e3ab 100644
--- a/lib/SimpleSAML/Utils/Auth.php
+++ b/lib/SimpleSAML/Utils/Auth.php
@@ -45,7 +45,7 @@ class Auth
     public static function getAdminLogoutURL(?string $returnTo = null): string
     {
         $as = new Authentication\Simple('admin');
-        return $as->getLogoutURL($returnTo = null);
+        return $as->getLogoutURL($returnTo);
     }