checkbox with empty label : how to get rid of the focus dotted square around the label

["Yannick Barbeaux" <ybarbeaux gmail com>]

I
want to display a list of checkboxes without label : the checkable squares only. So I logically set an empty string for the labels.

The problem I am facing is that when I check one of those boxes, a small dotted square appears on the right of the box (focus square) as it does around the label when it contains some text.
I would like this square not to appear because it is not aesthetic. (I tried to get the children of the checkbox (= label) and hide it but the dotted square still appears. And if I destroy the child, I face gtk errors).
Any suggestion to achieve hiding it?
Thanks in advance