Invalid SPF record for seznam.cz

seznam.cz has following invalid SPF record: v=spf1 mx a:212.80.76.43 ~all

Now should we be tolerant and accept "a:212.80.76.43" as "ip4:212.80.76.43",
or should we reject the whole record and return 'unknown'?

(There is legitimate mail from seznam.cz through their designated hosts,
and a lot of spam "from seznam.cz" through other hosts.)

Roger