RuntimeError when creating custom class with Dec 31st holiday

[ghost]

>>> from datetime import date
>>> import holidays
>>> 
>>> class TestHolidays(holidays.US):
...     def _populate(self, year):
...         holidays.US._populate(self, year)
...         self[date(year, 12, 31)] = "New Year's Eve"
... 
>>> '2014-12-31' in TestHolidays()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "holidays.py", line 79, in __contains__
    return dict.__contains__(self, self.__keytransform__(key))
  File "holidays.py", line 75, in __keytransform__
    self._populate(year)
  File "<stdin>", line 4, in _populate
  File "holidays.py", line 85, in __setitem__
    return dict.__setitem__(self, self.__keytransform__(key), value)
  File "holidays.py", line 75, in __keytransform__
    self._populate(year)
  File "<stdin>", line 4, in _populate
  File "holidays.py", line 85, in __setitem__
    return dict.__setitem__(self, self.__keytransform__(key), value))
...
  File "holidays.py", line 75, in __keytransform__
    self._populate(year)
  File "<stdin>", line 3, in _populate
  File "holidays.py", line 112, in _populate
    self[date(year, 1, 1)] = name
  File "holidays.py", line 85, in __setitem__
    return dict.__setitem__(self, self.__keytransform__(key), value)
  File "holidays.py", line 72, in __keytransform__
    year = (key + rd(days=+1)).year
RuntimeError: maximum recursion depth exceeded while calling a Python object