diff --git a/kiri-engine/Core/Str.php b/kiri-engine/Core/Str.php
index 435c125a..f8baf0ad 100644
--- a/kiri-engine/Core/Str.php
+++ b/kiri-engine/Core/Str.php
@@ -185,7 +185,7 @@ class Str
      * @return array
      * 剩余天，带分秒
      */
-    public static function timeout($endTime, int $startTime = NULL): array
+    public static function timeout($endTime, ?int $startTime = NULL): array
     {
         $endTime = $endTime - (!empty($startTime) ? $startTime : time());