Libvirtd not updating qemu config

I’ve put in my config

virtualisation.libvirtd.qemu.verbatimConfig = ''
  namespaces = []
  vnc_listen = "0.0.0.0"
'';

this builds with no errors, and I can verify the correct value loading the config into nix repl

yet this produces no change in /var/lib/libvirt/qemu.conf or influence libvirt/qemu in the way I’m after

Same issue here. I am trying to change the process user/group and it is not taking effect. In my case, I’ve got:

  virtualisation.libvirtd = {
    enable = true;
    qemu = {
      package = pkgs.qemu_kvm;
      runAsRoot = false;
      verbatimConfig = 
      ''
        namespaces = []
        user = "rob"
        group = "users"
      '';
    };
  };

Actually, I do see the change in /var/lib/libvirt/qemu.conf so my problem is different.