Image source forces top level directory to be lower case

If I create a top level directory and call it, say D (i.e., the full path is /D/) and then set the source of Image to be file://D/sample.gif  I receive the error: QML Image: Cannot open: file://d/sample.gif -> the D got converted to d internally.

Here is a very small sample code exhibiting that issue:

import QtQuick
Window {
    width: 640
    height: 480
    visible: true
    Image {
        anchors.fill: parent
        source: "file://D/sample.gif"
    }
}

I can work around this by setting file:/D/sample.gif or file:///D/sample.gif as source, but as far as I know these are technically invalid, aren't they?