diff --git a/app/Core/Model.php b/app/Core/Model.php
index deaa69d..95ff34f 100644
--- a/app/Core/Model.php
+++ b/app/Core/Model.php
@@ -193,7 +193,7 @@ class Model
      * @param string|null $col 过滤列（null 表示全表计数）
      * @param mixed       $val 过滤值
      */
-    public function count(string $col = null, $val = null): int
+    public function count(?string $col = null, $val = null): int
     {
         if (Db::driver() === 'mysql') {
             if ($col === null) {