bookpathalias for book-nodes of other types

Hi

The following is from http://drupal.org/node/144366#comment-769077

I had some problems with this feature in the Drupal 6.1 version. I used a 'page' node as an entry in a book. Then the node-type is not 'book'. And the bookpathalias will not be resolved. This is how i fixed it:

From line 400 pathauto.module:

<?php
// We're on a node and it's part of a book and it has book id set?  Get the book path alias
if (module_exists('book')) {
    if (isset($object->book) && !empty($object->book['bid']) && $object->nid != $object->book['bid']) {
    $values['bookpathalias'] = drupal_get_path_alias('node/'. $object->book['bid']);
  }
  else {
    $values['bookpathalias'] = '';
  }
}
?>

(edit:) Changed code: Don't generate bookpath alias if nid == bid

My problem is exactly the same but I am using 5.x

I've found the equivalent lines in book.module (100+) and tried edgar83s code but it doesn't work. I just don't know what needs changing for 5.x

Any help would be greatly appreciated.