[Interest] undefined as JS object key in QML?

[Jason H]

Simplified example:
Text {
    property var textForColor: {"transparent": "Waiting", "lime": "Ready", undefined: "Initializing"}
    text: textForColor[color]
    color: // set somewhere else, potentially undefined at the start
}

But if I include the undefined key, QML complains.
Fails execution with: Expected token `}'
If the undefined key-pair is first, then QtCreator complains that the colon after "transparent" as:
  Expected token `,'
If the undefined key-pair is last, then QtCreator complains that the colon after "transparent" as:
  Invalid property name "text"


However in Node it works just fine (JS REPL):
> var a = {undefined: "!", "1":"B"};
undefined
> a
{ '1': 'B', undefined: '!' }
> a[undefined]
'!'
> Object.keys(a)
[ '1', 'undefined' ]

Bug?
Sure there are ways to work around this (change undefined to be a string, and when indexing color, make that a string too) but shouldn't this be able to support it as undefined itself?