Pie chart invisible if all but one datum are 0

[henrypijames]

graph.type('pie');
graph.addSeries('A', [0, 1], 'red', 'none');
graph.addSeries('B', [2, 3], 'green', 'none');

The code above should produce two pie charts, the first of which is entirely green (a green circle). In reality, the first pie chart is invisible. Guess the 100% case needs special handling.