Nested table: separator problem

[Pool 475-1 FRD TE-N <Pool475-1.FRDTE-N@zf.com>]

Hi,

another question: why does my table (FO output) in the example below look
like this (although I set colsep's for the inner table to 0)? If I set
colsep on tgroup to 0, it works. Does anybody have an explanation for this?

----------------------------
|                          |
| test   | test     test   |
|                          |
----------------------------


Greetings,
Bjoern

Example:

<informaltable>
  <tgroup cols="1">
    <colspec colname="col1"/>
    <tbody>
      <row>
        <entry>
          <para>
            <informaltable frame="none">
              <tgroup cols="3">
                <colspec colname="col1" colsep="0"/>
                <colspec colname="col2" colsep="0"/>
                <colspec colname="col3" colsep="0"/>
                <tbody>
                  <row>
                    <entry>test</entry>
                    <entry>test</entry>
                    <entry>test</entry>
                  </row>
                </tbody>
              </tgroup>
            </informaltable>
          </para>
        </entry>
      </row>
    </tbody>
  </tgroup>
</informaltable>