Sectional edit don't set edit comment

if (sectionNumber != 0) {
  XWikiDocument sectionDoc = (XWikiDocument) tdoc.clone();
  sectionDoc.readFromForm((EditForm) form, context);
  String sectionContent = sectionDoc.getContent() + "\n";
  String content = doc.updateDocumentSection(sectionNumber, sectionContent);
  tdoc.setContent(content);
  tdoc.setTitle(title);
  // this line is missing
  tdoc.setComment(sectionDoc.getComment());
} else {
  tdoc.readFromForm((EditForm) form, context);
}