XUL and Unicode: button label

Hi Guys,

I have a button featuring a unicode character as a button label:

<button id="foo" label="&#9724;" />

The unicode character is displayed correctly upon loading of the xul
page.

Changing the value of the label fails, however via JS:

document.getElementById( "foo" ).label = "&#9654;" ;

The characters &#9654; are shown as the label, not the unicode
character.

Any iday, why this is failing or what the correct procedure would be
to reassign a unicode character code to the button label dynamically?

Thanks,

Paul