setting QHeaderView background image

Question

Im trying to set background-image for QHeaderView through a stylesheet. background-color works fine, but background-image does not.
I've used the same stylesheet on another widget and it works. But wont work on QHeaderView... My stylesheet is:

QHeaderView::section, QHeaderView
{
    background-image:url(:/topgradient.png);
    background-repeat:repeat-x;
}

Is it not possible the set QHeaderView's background image through stylesheet? How can I set it's background image?