.font("bold") on Wedge not working?

[wamci]

Trying to make my labels bold on a pie chart?

vis = Rubyvis::Panel.new.width(width).height(height)
    vis.add(pv.Wedge)
       .data(percentages)
       .bottom(radius)
       .left(radius)
       .outer_radius(radius)
       .angle(angle)
       .fill_style(colours)
       .anchor('center').add(pv.Label)
       .font("bold")
       .text_style('#000000')
       .text(labels)
       .text_angle(0)
    vis.render()

Thanks