MouseArea has no automatic refresh

import Qt 4.7

Item {
	width: 200; height: 200

	Rectangle { // square
		id: rect
		x: 40; y: 40; width: 48; height: 48
		color: ma.containsMouse ? "red" : "green"
		visible: false
		Text { text: "click!"; anchors.centerIn: parent }
		MouseArea {
			id: ma
			anchors.fill: parent
			hoverEnabled: true
			onClicked: rect.visible = false
		}
	}

	Rectangle { // button
		border.color: "black"
		x: 20; y: 100; width: 100; height: 24
		color: gray
		Text { text: "click me!"; anchors.centerIn: parent }
		MouseArea {
			anchors.fill: parent
			onClicked: rect.visible = !rect.visible
		}
	}
}