diff --git a/helpers/models.py b/helpers/models.py
index 6c3391e..9ad46c0 100644
--- a/helpers/models.py
+++ b/helpers/models.py
@@ -3,7 +3,7 @@ from dataclasses import dataclass
 from typing import Optional
 
 import marshmallow_dataclass
-from marshmallow import EXCLUDE, post_load
+from marshmallow import EXCLUDE, pre_load
 
 
 @dataclass
@@ -26,14 +26,13 @@ class Lesson:
     hse_id: int
 
 
-
 USchema = marshmallow_dataclass.class_schema(User)
 
 
 class UserSchema(USchema):
 
-    @post_load
-    def stringify_time(self, in_data, **kwargs):
-        if 'next_daily_notify_time' in in_data:
-            in_data['next_daily_notify_time'] = str(in_data['next_daily_notify_time'])
-        return in_data
+    @pre_load
+    def stringify_time(self, data, many, **kwargs):
+        if 'next_daily_notify_time' in data:
+            data['next_daily_notify_time'] = str(data['next_daily_notify_time'])
+        return data