OrderedList and 'continuation' attribute

Hi,

I'm having a problem with the 'continuation' attribute on <orderedlist> elements. When I set it to 'continues' and the list follows a nested list, the numbering is started from the nested list rather than the outer list. For example, if I have:

<orderedlist>
  <listitem><para>First Item</para></listitem>
  <listitem><para>Second Item</para></listitem>
  <listitem><para>Third Item</para>

                 <orderedlist>
                   <listitem><para>Nested First Item</para></listitem>

                   <listitem><para>Nested Second Item</para></listitem>

                   <listitem><para>Nested Third Item</para>
                   <listitem><para>Nested Fourth Item</para>

                   <listitem><para>Nested Fifth Item</para>

                 </orderedlist>

  </listitem>

</orderedlist>

<orderedlist continuation='continues'>
  <listitem><para>Fourth Item</para></listitem>

  <listitem><para>Fifth Item</para></listitem>

</orderedlist>

When transformed using the docbook XSL via FO to PDF the output looks like:

1. First Item

2. Second Item

3. Third Item
    a. Nested First Item
    b. Nested Second Item
    c. Nested Third Item
    d. Nested Fourth Item
    e. Nested Fifth Item

6. Fourth Item

7. Fifth Item

Maybe this is intended behaviour - but I want to have 6 & 7 actually numbered 4 & 5 so that they continue the numbering from the list at the same level. Does anyone know if/how I can add something to my customisation layer to change the behaviour here?

Thanks!

Howard