Weight not displayed in outline tab (for non book-nodes)

When you add a node of type page (NOT book page!) to a book via the outline feature of the node, you can of course assign a weight for that node. If you submit the form then, the weight is also correctly saved (verified by peeking into the DB with phpMyAdmin). Sadly, when you edit this node again and again use the outline tab, there will always be weight "0" preselected and not the weight you actually set for the page.