diff --git a/library/think/Validate.php b/library/think/Validate.php
index dc2457a4..1fe27d1f 100644
--- a/library/think/Validate.php
+++ b/library/think/Validate.php
@@ -11,6 +11,7 @@
 
 namespace think;
 
+use think\Db;
 use think\exception\ClassNotFoundException;
 use think\File;
 use think\Lang;