Menu list items with no nested lists have "collapsed" and "expanded" classes instead of "leaf"

It appears to be not only with the second-level list item but in the first level (or any further) as well.
Seems like the menu system treats action-links lists as nested menu lists and assigns "collapsed" and "expanded" classes to such menu list items.

And even more strange:
For example,
Administer > Structure:
Contact form ("leaf")

After clicking on Contact form it becomes... "expanded".

[edit]

Marking as duplicate of http://drupal.org/node/813736