DialogButtonBox.DestructiveRole doesn't close the dialog

import QtQuick 2.7
import QtQuick.Controls 2.3

ApplicationWindow {
    id: main
    visible: true
    width: 640
    height: 480

    Dialog {
        id: discardChangesDialog
        objectName: "discardChangesDialog"
        x: parent.width / 2 - width / 2
        y: parent.height / 2 - height / 2
        title: qsTr("Unsaved changes")
        modal: true
        visible: true

        onAccepted: print("saved")
        onDiscarded: print("discarded")

        Label {
            text: qsTr("The action you're about to perform could discard changes.\n\nContinue anyway?")
        }

        footer: DialogButtonBox {
            Button {
                objectName: "saveChangesDialogButton"
                text: qsTr("Save")
                DialogButtonBox.buttonRole: DialogButtonBox.AcceptRole
            }
            Button {
                objectName: "discardChangesDialogButton"
                text: qsTr("Discard")
                DialogButtonBox.buttonRole: DialogButtonBox.DestructiveRole
            }
        }
    }
}