Capital C can't be used as variable name

[nicoguaro]

I tried the following in SymPy Live

C = 3

and it gave me the following error message:

Exception in SymPy Live of type <type 'exceptions.NameError'>
for reference the last 5 stack trace entries are
Traceback (most recent call last):
  File "/base/data/home/apps/s~sympy-live-hrd/50.411508059631415177/shell.py", line 781, in post live.evaluate(statement, session, printer, stream)
  File "/base/data/home/apps/s~sympy-live-hrd/50.411508059631415177/shell.py", line 453, in evaluate if name not in old_globals or val != old_globals[name]:
  File "/base/data/home/apps/s~sympy-live-hrd/50.411508059631415177/sympy/sympy/core/numbers.py", line 2167, in __ne__ return not self == other
  File "/base/data/home/apps/s~sympy-live-hrd/50.411508059631415177/sympy/sympy/core/numbers.py", line 2164, in __eq__ return Rational.__eq__(self, other)
  File "/base/data/home/apps/s~sympy-live-hrd/50.411508059631415177/sympy/sympy/core/numbers.py", line 1747, in __eq__ other = _sympify(other)
NameError: name 'C' is not defined as a Symbol