Actually, there were two issues:- 'gridOn' state should always be contained in the _tick_kw settings.  This is needed because we support toggling via grid() and thus need  to be able to query the state. Therefore, the _tick_kw dicts must be  resetted instead of cleared.- grid(some_kwarg=...) i.e. with b=None and keywords must be treated  explicitly as b=True as the docs already propose.Closesmatplotlib#20149.