diff --git a/src/html_preprocessor.py b/src/html_preprocessor.py
index 27bcf3b..5af2226 100644
--- a/src/html_preprocessor.py
+++ b/src/html_preprocessor.py
@@ -3,8 +3,9 @@ import os
 import pathlib
 import re
 from shutil import copyfile
+from typing import List
 
-from bs4 import BeautifulSoup, NavigableString
+from bs4 import BeautifulSoup, NavigableString, Tag
 
 from livecarta_config import LawCartaConfig, BookLogger, BookStatusWrapper
 
@@ -675,7 +676,7 @@ class HTMLPreprocessor:
 
             self._process_headings()
 
-            self.content = self.body_tag.find_all(recursive=False)
+            self.content: List[Tag] = self.body_tag.find_all(recursive=False)
 
             self._process_lists()
             # delete text before table of content if exists