unable to set value for core.proxy_ignore_hosts

I want to set proxy to ams which works for proxy_http and proxy_https.

$ /snap/bin/ams.amc config set core.proxy_http http://192-168-1-0--24.maas-internal:8000/
$ /snap/bin/ams.amc config set core.proxy_https http://192-168-1-0--24.maas-internal:8000/

but it fails for proxy_ignore_hosts

$ /snap/bin/ams.amc config set core.proxy_ignore_hosts 127.0.0.1,192.168.1.127,::1,localhost
Error: argument config key is invalid

and the value is not set

$ /snap/bin/ams.amc config show
config:
......
  core.proxy_http: http://192-168-1-0--24.maas-internal:8000/
  core.proxy_https: http://192-168-1-0--24.maas-internal:8000/
  core.proxy_ignore_hosts: ""

one workaround is to set it to etcd directly.

$ sudo ETCDCTL_API=3 /snap/etcd/current/bin/etcdctl --cert=/var/snap/ams/common/etcd/client-cert.pem --key=/var/snap/ams/common/etcd/client-key.pem --insecure-transport=true --endpoints=192.168.1.84:2379 get /ams/1.0/config/core.proxy_ignore_hosts --prefix
/ams/1.0/config/core.proxy_ignore_hosts
{"version":0,"type":"config-item","data":{"name":"core.proxy_ignore_hosts","value":"127.0.0.1,192.168.1.127,::1,localhost"}}