ScriptUI button active blue marker

Hi

I'm making a ScriptUI panel. I have a icon button which is based on an png image I load:

var button = container.add("iconbutton",undefined, imagePath, {"style":"toolbutton"});

The image isn't a perfect square, so it contains transparent pixels. Problem is, when I click the button it gets the focus, and all that is transparent will be AE-blue until it looses focus again.

Is there a way to avoid this? I tried using the "active" property, but that didn't seem to do much.

If I just could control the focus on the button...

Any help is greatly appreciated,

Jakob