Unable to build bcachefs filesystem using image builder

[oott123]

nix:

boot.supportedFilesystems = [ "bcachefs" ];

with disko:

root = {
  size = "100%";
  content = {
    type = "filesystem";
    format = "bcachefs";
    mountpoint = "/";
  };
};

got:

+ mount /dev/disk/by-partlabel/disk-vda-root /mnt/ -t bcachefs -o defaults -o X-mount.mkdir
mount: /mnt/: unknown filesystem type 'bcachefs'.
       dmesg(1) may have more information after failed mount system call.

I have tried to adds:

disko.imageBuilder.extraRootModules = [ "bcachefs" ];

but with no luck:

       > root module: bcachefs
       > modprobe: FATAL: Module bcachefs not found in directory /nix/store/w46bkv4gwfrwrqlflbkl5j68kmv13l5i-kernel-modules/lib/modules/6.17.7

I think that's because the default kernel package don't includes the module I need (bacahefs in my case).