See my last paragraph: I propose to deliver a single patch that fixes both this bug and issue12675. I hope this is OK. (If you prefer, I'll try to split the patch in two.)

I just noticed another bug in untokenize(): in compatibility mode, if untokenize() is passed an iterator rather than a list, then the first token gets discarded:

    Python 3.3.0a0 (default:c099ba0a278e, Aug  2 2011, 12:35:03) 
    [GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)] on darwin
    Type "help", "copyright", "credits" or "license" for more information.
    >>> from tokenize import untokenize
    >>> from token import *
    >>> untokenize([(NAME, 'hello')])
    'hello '
    >>> untokenize(iter([(NAME, 'hello')]))
    ''

No-one's noticed this because the unit tests only ever pass lists to untokenize().