BGP session local capabilities / announced AF

Bird 2.0.10 I have BGP neighbors I only want to advertise ipv4 or ipv6 to, not both. It appears BIRD assumes both even though I only have either a ipv4 or ipv6 channel configured for the protocol. (not both) Is v4 implicit? If so, is there a way to negate that? Local capabilities Multiprotocol AF announced: ipv4 ipv6 -- inoc.net!rblayzor XMPP: rblayzor.AT.inoc.net PGP: https://pgp.inoc.net/rblayzor/