can not create a server with IPv4 and IPv6 fixed ip

i can not create a server with a fixed IPv4 and IPv6 in the same network but different subnets. I get the following error when using:

openstack server create --flavor x --image y --boot-from-volume 10 --nic net-id=<uuid-of-network>,v4-fixed-ip=<fixed-ipv4>,v6-fixed-ip=<fixed-ipv6> --key-name z --availability-zone a test-vm-name

i get the following error:
openstack server create: error: argument --nic: Invalid argument net-id=<uuid-of-network>,v4-fixed-ip=<fixed-ipv4>,v6-fixed-ip=<fixed-ipv6>; either 'v4-fixed-ip' or 'v6-fixed-ip' should be specified but not both

this seems to be hardcoded here: https://github.com/openstack/python-openstackclient/blob/902fb783424725434c20857d1dd1fef31ed4180e/openstackclient/compute/v2/server.py#L999

therefore it is not possible to create a vm with a dual stack directly. as a work around one would have to create the port before and attach it or leave the ipv6 address away and add it after creation.