Based on this commit into MySQL-5.7:
> commit 8e51b845aafc8b4cdebd763c8aebda262ac2d4cd
> Author: Guilhem Bichot <guilhem.bichot@oracle.com>
> Date:   Mon Nov 4 15:44:55 2013 +0100
>
>    Bug#13944462 'NULL IN (XX)' RETURNS WRONG RESULTS