Delete a DHCP lease in Foreman-Proxy DHCP using REST API

Foreman is our DHCP server with proxy dhcp enabled (isc-dhcp). I am trying to delete an active IP address lease using smart-proxy REST API:
curl -ks --tlsv1 --cacert /etc/puppetlabs/puppet/ssl/ca/ca_crt.pem --cert /etc/puppetlabs/puppet/ssl/certs/ --key /etc/puppetlabs/puppet/ssl/private_keys/ -X DELETE

This just shows:

IP_ADDRESS / MAC_ADDRESS is static - unable to delete

However there is a lease entry for that MAC address in dhcpd.leases.

Expected outcome:
Lease gets deleted from dhcpd.leases

Foreman and Proxy versions:

foreman                 1.20.2-1
foreman-cli             1.20.2-1
foreman-debug           1.20.2-1
foreman-installer       1.20.2-1
foreman-postgresql      1.20.2-1
foreman-proxy           1.20.2-1
ruby-foreman-hooks      0.3.14-1
ruby-hammer-cli-foreman 0.15.1-1

Distribution and version:
Ubuntu 18.04.2 LTS

Other relevant data:
proxy.log contents:

2019-11-18T23:16:38 1a3e10bb [I] Started DELETE /
2019-11-18T23:16:38 1a3e10bb [E] / XX:XX:XX:XX:XX:XX is static - unable to delete
2019-11-18T23:16:38 1a3e10bb [I] Finished DELETE / with 400 (0.67 ms)

Hello, leases cannot be deleted, they expire because DHCP client was already given a lease for some (limited) period. So all you need to do is just wait. ISC OMAPI does not provide a way to delete an existing lease I believe. You can’t even create leases using that API.