set_ylim() does not work with twinx()-axes

Hi,

I am plotting two graphs in one according to
http://matplotlib.sourceforge.net/examples/two_scales.py

I want the plot belonging to the right axis to start with y=0. However,

ax2.set_ylim(ymin=0.0)

does not affect the plot at all.

Any hints?

Regards,
wr