Just ran into this problem using Python 2.7.3 and the issue others mention in conjunction with Django.

Note the 2.7 docs still imply it's ASCII: http://docs.python.org/2/library/pickle.html#data-stream-format

It has a weak caveat "(and of some other characteristics of pickle‘s representation)", but if you only skim read the bullet points below you'll miss that.

Yes I will use base64 to get around this, but the point is the documentation is still unclear and should probably completely remove the reference to ASCII in favour of "human-readable"... or even better, explicitly mention what will happen with unicode.