http://bugs.python.org/review/16036/diff/6073/Doc/library/functions.rst File Doc/library/functions.rst (right): http://bugs.python.org/review/16036/diff/6073/Doc/library/functions.rst#newcode639 Doc/library/functions.rst:639: If *base* is given, then *x* must be a string. The string must be Somewhere should be exposed that x must be str, bytes, bytearray or a subclass. http://bugs.python.org/review/16036/