diff --git a/application/common/controller/Api.php b/application/common/controller/Api.php
index f685ca20..38a226d9 100644
--- a/application/common/controller/Api.php
+++ b/application/common/controller/Api.php
@@ -69,7 +69,7 @@ class Api
      * @access public
      * @param Request $request Request 对象
      */
-    public function __construct(Request $request = null)
+    public function __construct(?Request $request = null)
     {
         $this->request = is_null($request) ? Request::instance() : $request;