pygmt: pygmt.Figure.meca offset not working

I am using pygmt to graph focal mechanisms with magnitude scale. However, when I try to give it an offset so that they don’t pile up the function doesn’t seem to work.

I’m using :

spec = dict (strike=strikes[0], dip=dips[0], rake=rakes[0], magnitude=magnitude [0])

fig.meca (spec, scale=f ".{0.002 * (2 ** magnitude[0])}c", longitude = lons [0], latitude = lats [0], depth = 25.0, convention = "aki", plot_longitude = lons [0], plot_latitude = lats[0] -10, offset=True) 

where all the objects are lists with real (float) values

System information

# Name                    Version                   Build  Channel
pygmt                     0.3.1              pyhd8ed1ab_0    conda-forge

Do I make something wrong?