Check box for a binary attribute
I'm experiencing an issue concerning a product attribute display. I need a binary checkbox, meaning a kind of "Yes" if checked or "No" if not. When I add a new attribute to a product type, I choose a field "List (text)" and a "Checkbox/Radio button" widget. As attribute list I just put "Yes", and choose "show in the add to cart as an attribute" "Checkbox/Radio button".
At this point, I get a radio button for my attribute, meaning that when it is selected, I cannot deselect it. Any idea ?
Thanks for your help...