Hi.
In docbook output, given something like this input:
....
@node Concept Index
@unnumbered Index
@printindex cp
@bye
The generated docbook is
....
</chapter>
<chapter label="" id="Concept-Index">
<title>Index</title>
<index role="cp"></index>
</chapter>
</book>
This isn't valid docbook. It should be
....
</chapter>
<index role="cp"></index>
</book>
The <index> tag could be
<index role="cp"/>
but that is a minor quibble.
Removing the @node and @unnumbered don't help, then we get the
<index> tag before the </chapter> tag and it needs to come after it.
Thanks!
Arnold