DOCBOOK-APPS: table span problem

[Tim =?iso-8859-15?q?Terleg=E5rd?= <tim at se dot linux dot org>]

What's wrong with the table below? I want the table to be 2x3 and so it is. I 
also want the "Host-to-network" entry to span both rows, but I don't succeed. 
There is still a border drawn between first and second row in column 3.
What am I doing wrong? (using DSSSL 1.72 and sgml->tex->pdf)

<table>
  <title>The OSI and TCP/IP reference models.</title>
  <tgroup cols="3" align="left" colsep="1" rowsep="1">
  <thead>
  <row>
    <entry></entry>
    <entry>OSI</entry>
    <entry>TCP/IP</entry>
  </row>
  </thead>
  <tbody>
  <row>
    <entry>2</entry>
    <entry>Data-Link</entry>
    <entry morerows="1" rowsep="0">Host-to-network</entry>
  </row>
  <row>
    <entry>1</entry>
    <entry>Physical</entry>
  </row>
  </tbody>
  </tgroup>
</table>

Thanks,

Tim