Windows: ComboBox not always correctly rendered in a layout

import QtQuick 2.1
import QtQuick.Controls 1.0
import QtQuick.Layouts 1.0

ColumnLayout {
    Label {
        text:"Resize the window and look at the combo box"
        Layout.alignment: Qt.AlignHCenter | Qt.AlignVCenter
    }
    ComboBox {
        model: 5
        Layout.alignment: Qt.AlignVCenter | Qt.AlignHCenter
    }
}