How to remove offset of axis in matplotlib 3d plot?

import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.gca(projection='3d')
ax.set_xlim([0, 1])

plt.show()

results in the following plot:

There is a small margin between the axis and there limits.
How can I get rid of this offset of the axis.
For example ax.set_xlim([0, 1]) has not effect!