dnssec-keymgr fails to apply policy

[Lefteris Tsintjelis]

I am using FreeBSD with bind v9.11.8. v9.11.6P1 also had the same problem.

I am using ECDSAP256SHA256 for ZSK and KSK. I have made a very simple 
policy that I am trying to automate by using dnssec-keymgr in crontab.

policy default {
         directory "/usr/local/etc/namedb/keys";
         algorithm ECDSAP256SHA256;
         pre-publish zsk 1w;
         post-publish zsk 1w;
         roll-period zsk 2mo;
};

zone example.com {
         policy default;
};

However, every time I run:

dnssec-keymgr -K /usr/local/etc/namedb/keys -r /dev/random

I always get this message:

Unable to apply policy: example.com/ECDSAP256SHA256: unsupported operand 
type(s) for +: 'float' and 'NoneType'

Any ideas what this may be?