lazy subchain protocol propagation is broken for icmpv6-type

[elho]

Given the minimal example

domain ip6 {
    table filter {
	chain INPUT {
	    proto icmpv6 subchain "test" {
		icmpv6-type echo-request ACCEPT;
	    }
	}
    }
}

ferm 2.5.1 as well as current git cause ip6tables to fail with unknown option "--icmpv6-type" error.
They do generate this command:

/usr/sbin/ip6tables-legacy -t filter -A test --icmpv6-type echo-request --jump ACCEPT

Whereas ferm 2.4 generates the correct command including the needed --protocol icmpv6:

/sbin/ip6tables -t filter -A test --protocol icmpv6 --icmpv6-type echo-request --jump ACCEPT