set xticks when using twinx()

Hello,

I to set custom xticks is usually used

fig = plt.figure()
ax1 = fig.add_subplot(xticks=[10,40,90])
plt.plot(range(100))

I now need to have a second y-axis and tried

fig = plt.figure()

ax1 = fig.add_subplot(xticks=[10,40,90])
plt.plot(range(100))

ax2 = plt.twinx()
plt.plot([x*x for x in range(100)])

which works fine, but i use the ability to manipulate the xticks.

Any help is highly appriciated.

Thank you, Mario.