MouseArea drag threshold doesn't work with preventStealing

import QtQuick 2.6
import QtQuick.Controls 1.4

ApplicationWindow {
    id: root
    visible: true
    width: 400
    height: 400

    MouseArea {
        id: mousearea
        anchors.fill: parent
        drag.target: rectangle
        drag.threshold: 100
        propagateComposedEvents: true
        preventStealing: true
    }

    Rectangle {
        id: rectangle
        color: "red"
        width: 30
        height: width
    }
}