diff --git a/src/calibre/ebooks/docx/writer/from_html.py b/src/calibre/ebooks/docx/writer/from_html.py
index 16283c085f..a7ed841b78 100644
--- a/src/calibre/ebooks/docx/writer/from_html.py
+++ b/src/calibre/ebooks/docx/writer/from_html.py
@@ -586,7 +586,7 @@ class Convert:
         else:
             text = html_tag.text
             is_list_item = tagname == 'li'
-            has_sublist = is_list_item and len(html_tag) and barename(html_tag[0].tag) in ('ul', 'ol') and len(html_tag[0])
+            has_sublist = is_list_item and len(html_tag) and isinstance(html_tag[0].tag, str) and barename(html_tag[0].tag) in ('ul', 'ol') and len(html_tag[0])
             if text and has_sublist and not text.strip():
                 text = ''  # whitespace only, ignore
             if text: