Issues setting up NPTv6

My ISP provides me a /64 for IPv6, which means I can’t get IPv6 working on my Wireguard peers.

I’m trying to setup Symmetric dynamic NPTv6 following the steps here

But I’m getting this error

Error: syntax error, unexpected '}'
add rule inet fw4 srcnat oifname eth0 snat ip6 prefix to ip6 saddr map { fd27:dfec:1903::/60 :  }
                                                                                                ^
Error: syntax error, unexpected colon
add rule inet fw4 srcnat oifname br-lan snat ip6 prefix to ip6 saddr map {  : fd27:dfec:1903::/60 }
                                                                            ^
Include '/etc/nftables.d/npt6.sh' failed with exit code 1

Any reason why it’s failing to get my wan6 address? My router does have it, as seen in luci and after running ifstatus wan6.