Overriding Dialog's contentItem with a ColumnLayout that contains one item breaks DialogButtonBox's layouting

import QtQuick 2.7
import QtQuick.Controls 2.3
import QtQuick.Layouts 1.3

ApplicationWindow {
    visible: true
    width: 500
    height: 500

    Dialog {
        id: dialog
        objectName: "imageSizePopup"
        title: qsTr("Choose a size for the image")
        modal: true
        dim: false
        focus: true
        closePolicy: Popup.CloseOnEscape | Popup.CloseOnReleaseOutside
        visible: true

        contentItem: ColumnLayout {
            Item {
                Layout.preferredHeight: 4
            }
        }

        standardButtons: Dialog.Ok | Dialog.Cancel
//        footer: DialogButtonBox {
//            Button {
//                objectName: "imageSizePopupOkButton"
//                text: "OK"

//                DialogButtonBox.buttonRole: DialogButtonBox.AcceptRole

//                onClicked: {
//                    project.resize(widthSpinBox.value, heightSpinBox.value, smoothCheckBox.checked);
//                    dialog.visible = false;
//                }
//            }
//            Button {
//                objectName: "imageSizePopupCancelButton"
//                text: "Cancel"

//                DialogButtonBox.buttonRole: DialogButtonBox.DestructiveRole

//                onClicked: dialog.visible = false
//            }
//        }
    }
}