diff --git a/dao/user.go b/dao/user.go
index a725174..7da04ed 100644
--- a/dao/user.go
+++ b/dao/user.go
@@ -116,6 +116,10 @@ func AddUserSync(req proto.UserAddOrUpdate) uint {
 	if res.Error != nil {
 		return 0
 	}
+	res = DB.Exec("update users set created_at=null where id=?", req.ID)
+	if res.Error != nil {
+		return 0
+	}
 	return req.ID
 }
 
@@ -125,6 +129,10 @@ func UpdateUserSync(req proto.UserAddOrUpdate) uint {
 	if res.Error != nil {
 		return 0
 	}
+	res = DB.Exec("update users set created_at=null where id=?", req.ID)
+	if res.Error != nil {
+		return 0
+	}
 	return req.ID
 }