`response-ip` settings in unbound - missing respip module

[yakatz]

We have a lot of 1:1 NAT IPs and rather than use NAT reflection or Split DNS, I would like to have the DNS server modify the response based on the returned A record.

I tried the following unbound custom configuration, but pfSense says it is invalid - reading the documentation, I can't figure out why:

server:
response-ip: xxx.xxx.xxx.xxx/32 redirect
response-ip-data: xxx.xxx.xxx.xxx/32 "A 192.168.118.31"

The configuration is validated, but unbound still won't start. The error in the logs is:

fatal error: response-ip options require respip module

Is there a way to load that module?