Material Button missing checked state visuals

import QtQuick 2.6
import QtQuick.Controls 2.0

ApplicationWindow {
    width: 800
    height: 400
    visible: true

    Grid {
        columns: 3
        spacing: 20
        anchors.centerIn: parent

        Button { text: "Normal" }
        Button { text: "Down";     down: true }
        Button { text: "Disabled"; enabled: false }

        Button { text: "Checked";  checked: true }
        Button { text: "Down";     checked: true; down: true }
        Button { text: "Disabled"; checked: true; enabled: false }

        Button { text: "Highlighted"; highlighted: true }
        Button { text: "Down";        highlighted: true; down: true }
        Button { text: "Disabled";    highlighted: true; enabled: false }

        Button { text: "Hi-checked"; highlighted: true; checked: true }
        Button { text: "Down";       highlighted: true; checked: true; down: true }
        Button { text: "Disabled";   highlighted: true; checked: true; enabled: false }
    }
}