diff --git a/framework/core/src/Mail/Mailer.php b/framework/core/src/Mail/Mailer.php
index dbdd0e87f8..c68bad46a3 100644
--- a/framework/core/src/Mail/Mailer.php
+++ b/framework/core/src/Mail/Mailer.php
@@ -21,7 +21,7 @@ public function __construct(
         string $name,
         Factory $views,
         TransportInterface $transport,
-        Dispatcher $events = null,
+        ?Dispatcher $events = null,
         protected SettingsRepositoryInterface $settings
     ) {
         parent::__construct($name, $views, $transport, $events);