QQuickLoader: the loaded item is not resized as appropriate

The Loader documentation states:

If the size of the Loader is specified explicitly by setting the width, height or by anchoring, the loaded item will be resized to the size of the Loader.

However, in the following test case, the loaded item does not get a proper size. In fact, it stays at (0,0) unless you uncomment the "anchors.fill: parent" statement, which should not be necessary because the loaded item is supposed to follow the size of the loader.

import QtQuick 2.0

Loader {
    id: loader

    width: implicitWidth
    height: implicitHeight

    sourceComponent: Rectangle {
        color: "green"
        implicitWidth: 240
        implicitHeight: 120
        //anchors.fill: parent
    }
}

To clarify, the window content should be green when it's working correctly.