column spanning issue

Note that I have removed all attributes except number-columns-spanned, for
brevity's sake. I have also removed rows around the one causing the problem.

Given the following docbook fragment:

<informaltable frame="none">
  <tgroup cols="16" align="left" colsep="1" rowsep="0">
    <colspec colname="c1" colwidth=".4in"/>
    <colspec colname="c2" colwidth=".4in"/>
    <colspec colname="c3" colwidth=".4in"/>
    <colspec colname="c4" colwidth=".4in"/>
    <colspec colname="c5" colwidth=".4in"/>
    <colspec colname="c6" colwidth=".4in"/>
    <colspec colname="c7" colwidth=".4in"/>
    <colspec colname="c8" colwidth=".4in"/>
    <colspec colname="c9" colwidth=".4in"/>
    <colspec colname="c10" colwidth=".4in"/>
    <colspec colname="c11" colwidth=".4in"/>
    <colspec colname="c12" colwidth=".4in"/>
    <colspec colname="c13" colwidth=".4in"/>
    <colspec colname="c14" colwidth=".4in"/>
    <colspec colname="c15" colwidth=".4in"/>
    <colspec colname="c16" colwidth=".4in"/>
    <tbody>
      <row>
        <entry align="center" namest="c1" nameend="c4">VER</entry>
        <entry align="center" namest="c5" nameend="c8">FAM</entry>
        <entry align="center" namest="c9" nameend="c16">PARTNO</entry>
      </row>
    </tbody>
  </tgroup>
</informaltable>

I expect the following output from the docbook.fo stylesheet:

<!-- table markup trimmed for brevity's sake -->
<fo:table-cell number-columns-spanned="4">
  <fo:block>VER</fo:block>
</fo:table-cell>
<fo:table-cell number-columns-spanned="4">
  <fo:block>FAM</fo:block>
</fo:table-cell>
<fo:table-cell number-columns-spanned="8">
  <fo:block>PARTNO</fo:block>
</fo:table-cell>

<!-- table markup trimmed for brevity's sake -->

Instead, I get this:

<!-- table markup trimmed for brevity's sake -->
<fo:table-cell number-columns-spanned="4">
  <fo:block>VER</fo:block>
</fo:table-cell>
<fo:table-cell number-columns-spanned="4">
  <fo:block>FAM</fo:block>
</fo:table-cell>
<fo:table-cell>
  <fo:block>PARTNO</fo:block>
</fo:table-cell>
<fo:table-cell>
  <fo:block/>
</fo:table-cell>
<fo:table-cell>
  <fo:block/>
</fo:table-cell>
<fo:table-cell>
  <fo:block/>
</fo:table-cell>
<fo:table-cell>
  <fo:block/>
</fo:table-cell>
<fo:table-cell>
  <fo:block/>
</fo:table-cell>
<fo:table-cell>
  <fo:block/>
</fo:table-cell>
<fo:table-cell>
  <fo:block/>
</fo:table-cell>
<fo:table-cell>
  <fo:block/>
</fo:table-cell>
<!-- table markup trimmed for brevity's sake -->

Note that, in addition to not spanning, the number of cells is wrong (9
rather than 8).

What caused this and what can I do about it?

Thanks.

Jay Bryant
Bryant Communication Services