Y regions not shown on certain values of data

to reproduce:
open http://c3js.org/samples/region.html page and put this values in data columns:

var chart = c3.generate({
data: {
columns: [
['data1', 0.00000001, 0.000000000000000000001, 0.000002, 0.00000001, 0.00000001, 0.00000001, 0.00000001]
]
},
regions: [
{axis: 'y', start: 50, class: 'regionY'},
{axis: 'y', start: 0, end:50, class: 'regionX'},
]
});

region is not shown.
Try to change 0.000002 to 0.00002 you can see that regionX starts not at 0, but somewhere below. When adding values after 2, like 0.0000224 regionX starts before 0...
Probably some tick and padding problem.