perfdhcp -4 can't request options via option 55 Parameter Request List

Trying to request options from the server.

perfdhcp -6 -o 6,1234 works.

perfdhcp -4 -o 55,1234 does not.

ERROR: running perfdhcp: Option 55 already present in this message.

The culprit seems to be an empty option 55 automatically added to all packets.

    // Set options: DHCP_MESSAGE_TYPE and DHCP_PARAMETER_REQUEST_LIST
[...]
    pkt4->addOption(Option::factory(Option::V4,
                                    DHO_DHCP_PARAMETER_REQUEST_LIST));

Question is why is this done?

Does not replicate on v6 because options are not required to be unique on v6, but empty option 6 is added there as well.

Fix is supposedly as easy as removing the addOption line. To be investigated.