It sounds like you're seeing the difference between this:

>>> n = -7
>>> n ** 0
1

and this:

>>> -7 ** 0
-1

This isn't a bug;  it's to do with how Python expressions are parsed:  in the second case, the expression is grouped as -(7 ** 0) rather than (-7) ** 0.

BTW, it's helpful to post exact code when filing a possible bug. :-)