FOP 0.93 Span="inherit" warning

["T.G. Mutato" <throw6617@gmail.com>]

I've been using DocBook 4.5, XSL 1.72.0 and FOP 0.93 on Windows and
noticed that whenever I run FOP on my DocBook source, I get the
following:

WARNING: span="inherit" on fo:block, but no explicit value found on
the parent FO.

Here's a simple example that demonstrates the warning:

<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd";>
<book>
  <bookinfo>
    <title>My First Book</title>
    <author><firstname>Jane</firstname><surname>Doe</surname></author>
    <copyright><year>1998</year><holder>Jane Doe</holder></copyright>
  </bookinfo>
  <chapter id="chapterone">
    <title id="atitleid">
      <indexterm>
        <primary>a nice index entry</primary>
      </indexterm>
      Here's our Chapter Title
    </title>
    <sect1 id="sectionone">
      <title>
        <indexterm>
          <primary>anothter nice index entry</primary>
        </indexterm>
        Here's our Section Title
      </title>
      <para>
        Lorem ipsum dolor sit amet, consectetuer adipiscing elit. In
tortor nibh, facilisis ac, consectetuer eget, malesuada
        molestie, augue. Etiam non nibh eget elit tincidunt commodo.
      </para>
    </sect1>
  </chapter>
  <index id="index"/>
</book>

Run the two commands:
xsltproc --output testbook.fo pdfdoc.xsl testbook.xml
fop.bat -fo testbook.fo -pdf testbook.pdf

and you see the Warning output.

The warning doesn't seem to be serious and I am not sure if it is an
issue with the FO stylesheets or with FOP. Is there a good way to turn
off the warning?

Thanks,
tgm