Binding to CheckBox::checked does not work as expected

import QtQuick 2.1
import QtQuick.Controls 1.0

Item {
    width: 360
    height: 360

    Column {
        spacing: 20
        anchors.centerIn: parent

        CheckBox {
            id: cb
            text: "Enabled"
        }

        CheckBox {
            checked: cb.checked // breaks after the first change
            enabled: false
            text: "Disabled"
        }
    }
}