Changing Image Radio Buttons Font Size

I am using the Image Radio Buttons widget, and whenever I make the images larger than 80px, then the image label font size is changed to 4px.  I tried adding the custom CSS to the widget, but I must be entering it wrong because I am still not able to change the size.

Please insert this CSS Code inside the widget:

span {
font-size: 12px !important;
}

Hope that helps. Thank you.

That worked.  Thank you!