diff --git a/src/epub_converter.py b/src/epub_converter.py
index c50dc40..056deb1 100644
--- a/src/epub_converter.py
+++ b/src/epub_converter.py
@@ -304,9 +304,11 @@ class EpubConverter:
             soup = self.href2soup_html[toc_href]
             for internal_link_tag in soup.find_all('a', {'href': internal_link_reg2}):
                 a_tag_href, a_tag_id = internal_link_tag.attrs['href'].split('#')
-                a_tag_href = a_tag_href or toc_href
                 # find full path
-                a_tag_href_matched_to_toc = self.match_href_to_path_from_toc(toc_href, a_tag_href, internal_link_tag)
+                if a_tag_href:
+                    a_tag_href_matched_to_toc = self.match_href_to_path_from_toc(toc_href, a_tag_href, internal_link_tag)
+                else:
+                    a_tag_href_matched_to_toc = os.path.normpath(toc_href).replace('\\', '/')
                 if not a_tag_href_matched_to_toc:
                     continue
                 new_id = self._create_unique_id(a_tag_href_matched_to_toc, a_tag_id)