pf: pfi_kif_unref: rules refcount <= 0

[Comète]

Hi,

I run OpenBSD 6.0 GENERIC.MP#4 amd64 on a firewall and I recently discovered 
lots of these messages in
dmesg:

pf: pfi_kif_unref: rules refcount <= 0

do you know what it is ?

Thanks

Morgan