Using Image.PreserveAspectFit results in inconsistent implicit/source size

import QtQuick 1.1

Item {
    width: 640
    height: 480

    MouseArea {
        property bool clicedOnce: false
        anchors.fill: parent
        onClicked: {
            print("BEFORE")
            print("\timplicitWidth: " + image.implicitWidth + " (sourceSize.width is " + image.sourceSize.width + ")")
            print("\timplicitHeight: " + image.implicitHeight + " (sourceSize.height is " + image.sourceSize.height + ")")

            if(!clicedOnce) {
                print("Setting image width")
                image.width = image.implicitWidth/2;
            }
            else {
                print("Setting image height")
                image.height = image.implicitHeight/2;
            }

            clicedOnce = true;

            print("AFTER")
            print("\timplicitWidth: " + image.implicitWidth + " (sourceSize.width is " + image.sourceSize.width + ")")
            print("\timplicitHeight: " + image.implicitHeight + " (sourceSize.height is " + image.sourceSize.height + ")")
            print("")

        }
    }

    Image {
        id: image

        source: "stretchbench/images/testIcon.png"
        fillMode: Image.PreserveAspectFit
    }
}

BEFORE
	implicitWidth: 49 (sourceSize.width is 49)
	implicitHeight: 57 (sourceSize.height is 57)
Setting image width
AFTER
	implicitWidth: 49 (sourceSize.width is 49)
	implicitHeight: 28.5 (sourceSize.height is 28)

BEFORE
	implicitWidth: 49 (sourceSize.width is 49)
	implicitHeight: 28.5 (sourceSize.height is 28)
Setting image height
AFTER
	implicitWidth: 49 (sourceSize.width is 49)
	implicitHeight: 28.5 (sourceSize.height is 28)

BEFORE
	implicitWidth: 49 (sourceSize.width is 49)
	implicitHeight: 57 (sourceSize.height is 57)
Setting image width
AFTER
	implicitWidth: 24.5 (sourceSize.width is 49)
	implicitHeight: 28.5 (sourceSize.height is 57)

BEFORE
	implicitWidth: 24.5 (sourceSize.width is 49)
	implicitHeight: 28.5 (sourceSize.height is 57)
Setting image height
AFTER
	implicitWidth: 12.25 (sourceSize.width is 49)
	implicitHeight: 14.25 (sourceSize.height is 57)