diff --git a/library/think/Process.php b/library/think/Process.php
index 6f3faa31..7348be47 100644
--- a/library/think/Process.php
+++ b/library/think/Process.php
@@ -123,7 +123,7 @@ class Process
      * @throws \RuntimeException
      * @api
      */
-    public function __construct($commandline, $cwd = null, array $env = null, $input = null, $timeout = 60, array $options = [])
+    public function __construct($commandline, $cwd = null, ?array $env = null, $input = null, $timeout = 60, array $options = [])
     {
         if (!function_exists('proc_open')) {
             throw new \RuntimeException('The Process class relies on proc_open, which is not available on your PHP installation.');