Declarative: "Unable to assign to undefined value" when attaching the anchors of a list view delegate to its parent

See the Qml example in bug #QTBUG-10353 ( http://bugreports.nokia.troll.no/browse/QTBUG-10353 ) to reproduce the problem.

This happens when I have something like:
Component {
id: delegate
Rectangle {
anchors.left: parent.left
anchors.right: parent.right
...

It actually works, I get the expected result which is having the rectangle in the delegate span on all the horizontal space.
However I get a ton of these warnings anyway while scrolling and I can't see the other stuff I want to see in the debug output.