nid = 0 after book page import

I'm trying to add import/export support to one of my modules, but ran into problems getting nid updated. So I started playing around with book page, since it uses a similar structure. I created a simple book page and exported it to xml using the predefined definition, but when I imported the node again, it ended up with nid=0 in the book table.

The vid field is updated ok, so I tried to add '#reference_field' => array('revisions', 'nid') to the book_nid definition (similar to the definition of book_vid), since the field isn't named book_nid in the reference entity. But that didn't make any difference.

Changing to definition to

works as long as you are importing the page into the existing node. But if you then make a 'keyless' import (ie. strip away all ids and change all occurences of the title, see attachment) to import as a new node, nid is again 0 in the book table.

This issue might be somewhat related to http://drupal.org/node/93179