"model.value.childvalue" value not change in ListModel::delegate

import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3
import QtGraphicalEffects 1.0

ApplicationWindow {
	visible: true
	width: 640
	height: 480
	title: qsTr("Hello World")

	ColumnLayout {
		anchors.fill: parent
		ListView {
			anchors.fill: parent
			model: ListModel {
				id: listmodel
				}

			Component.onCompleted: {
				listmodel.append({
					text: "Image 1",
					image: { value: "picture.png1", imageType: 1 },
					position: 1
				});
				listmodel.append({
					text: "Image 2",
					image: { value: "picture.png2", imageType: 1 },
					position: 2
				});
				listmodel.append({
					text: "Image 1",
					image: { value: "picture.png3", imageType: 1 },
					position: 3
				});
			}

			delegate: Item {
				width: parent.width
				height: 50

				RowLayout {
					anchors.fill: parent
					Text {
						text: model.text
					}
					Text {
						text: model.image.value
					}
				}
			}
		}
		Button {
			text: "test"
			onClicked: {
				var m = listmodel.get(0)
				m.text = "aaaa" // change in model
				m.image.value = "zzzz" // not change! right?

				var image = m.image
				image.value = "ddd" // not change
				m.image = image // change in model

				var test = { a: { b: "c" } }
				test.a.b = "e" // its change!
				console.log( test.a.b )
				test.a.b = "d"
				console.log( test.a.b )
			}
		}
	}
}