Accessing a sheet in a style element in an svg element

Dear SVG working group!

I just tried to access a sheet in a style added to an svg element:

    var theSvg = document.createElementNS("http://www.w3.org/2000/svg",
"svg");
    var theStyle = document.createElementNS("http://www.w3.org/2000/svg",
"style");
    theSvg.appendChild(theStyle);
    console.log("theStyle.sheet=", theStyle.sheet); // undefined, try
adding svg to DOM
    document.body.appendChild(theSvg);
    console.log("theStyle.sheet=", theStyle.sheet); // still undefined

As you can see this failed. I have little knowledge of this subject, but
was directed here from my question here:
http://stackoverflow.com/questions/24920186/how-do-i-create-a-style-sheet-for-an-svg-element

I am not sure if a specification is lacking here or if this is a bug in the
browsers implementation. However this must of course be a part of the
specification for using CSS with SVG.

Kind regards,
L