Tree selection - icon transparency (lack of)

I have a QTreeWidget for which several branches have an attached Icon set via setIcon().

When that particular branch is selected the icon image ends up with a square colored
area around it. I want just the circular colored ball to show under the selection.

I know this is some sort of a transparency issue, but I have no idea how to easily address
this.

Is this something i can control by editing the image itself?

It looks like you have to provide a "selected" version of your icon. See QIcon::addPixmap().