Combining/compacting 2 rules into 1

["William N." <netfilter@riseup.net>]

Hello,

I am trying to "compact" the following rules:

table netdev filter {
	chain ingress {
		type filter hook ingress device "eth0" priority -500;
		# ...

		meta protocol ip \
			tcp flags syn \
			tcp option maxseg size lt 536 \
			log prefix "TCP MSS: " \
			counter packets 0 bytes 0 \
			drop

		meta protocol ip6 \
			tcp flags syn \
			tcp option maxseg size lt 1220 \
			log prefix "TCP MSS: " \
			counter packets 0 bytes 0 \
			drop
	}
}

into something like:

table netdev filter {
	chain ingress {
		type filter hook ingress device "eth0" priority -500;
		# ...

		meta protocol tcp option maxseg size map lt {
				ip : 536,
				ip6 : 1220
			} \
			tcp flags syn \
			log prefix "TCP MSS: " \
			counter packets 0 bytes 0 \
			drop
	}
}

but I am getting errors, as my syntax is obviously wrong. The first error is:

Error: syntax error, unexpected size, expecting newline or semicolon
                meta protocol tcp option maxseg size map lt {
                                                ^^^^

What is the correct syntax for this?