Error on first readchunk with GridOut(_connect=False)

>>> g = GridOut(db.fs, f._id, _connect=False)

>>> g.readchunk()

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

  File "gridfs/grid_file.py", line 446, in readchunk

    chunk_size = int(self.chunk_size)

  File "gridfs/grid_file.py", line 438, in __getattr__

    raise AttributeError("GridOut object has no attribute '%s'" % name)

AttributeError: GridOut object has no attribute 'chunk_size'