> > This is not compliant with how the PEP defines it (the frame size doesn't
> > include the header of the next frame):
> > http://www.python.org/dev/peps/pep-3154/#framing
> 
> "How the pickler decides to partition the pickle stream into frames is an 
> implementation detail."

Of course, but it still has to respect the frame structure shown in the
ASCII art drawing.

> Could you write tests which exposes behavior difference without sticking 
> implementation details?

That's a good idea. At least I'll open an issue for it.