diff --git a/utils/wechat/message_to_db.py b/utils/wechat/message_to_db.py
index b33bcda..deeaa0c 100644
--- a/utils/wechat/message_to_db.py
+++ b/utils/wechat/message_to_db.py
@@ -517,7 +517,8 @@ class MessageStorage:
         import xml.etree.ElementTree as ET
 
         # 按日期和时间分组
-        time_groups = defaultdict(lambda: defaultdict(list))
+        # 结构: {date_key: {time_key: {sender_name: [contents]}}}
+        time_groups = defaultdict(lambda: defaultdict(lambda: defaultdict(list)))
         dates_included = set()  # 记录出现的日期
 
         for msg in messages: