diff --git a/src/Router.php b/src/Router.php
index 3a0974b..3fe855b 100644
--- a/src/Router.php
+++ b/src/Router.php
@@ -27,7 +27,7 @@ class Router extends BaseRouter
     /**
      * {@inheritdoc}
      */
-    public function __construct(Dispatcher $events, Container $container = null)
+    public function __construct(Dispatcher $events, ?Container $container = null)
     {
         parent::__construct($events, $container);