indexentries freak out .xml->.fo (bug?)

Hi; feeding what-look-to-me-like-dull <indexentry>s, e.g.

   <sect2 id="r-use-booleans">
   <title>Booleans are building blocks</title>
   <indexterm>
     <primary>Boolean</primary>
   </indexterm>
   ...

into xsltproc w/ docbook-xsl-1.65.1, I get: the document
xmllint's OK, and it goes to chunked html OK; *but* when
going to FO with <xsl:import
href="[snip]/xsl/current/fo/profile-docbook.xsl"/>,
I suddenly get lots of...

   Request for title of element with no title: indexterm
   Request for label of unexpected element: indexterm

and the titles for everything are basically hosed.

If I lose profiling, and go with <xsl:import
href="[snip]/xsl/current/fo/docbook.xsl"/>, it behaves as
expected.

That smells like a bug (happy to cooperate in fixing it),
but would welcome any other insights.  Thanks,

Will