Help setup with nixld and Neovim

[minizilla]

Description

I'm using Neovim with the following setup

local nvim_lsp = require("lspconfig")
nvim_lsp.nixd.setup({
   cmd = { "nixd" },
   settings = {
      nixd = {
         formatting = {
            command = { "nixfmt" },
         },
      },
   },
})

When try to format the nix file, nothing happened, no formatting, check with nixfmt -c flake.nix also report flake.nix: not formatted.

Previously I'm using nixpkgs-fmt, the formatter is worked well.
Can you help me how to setup nixfmt with nixld and Neovim?

[infinisil]

Can you make sure that you installed a recent version of nixfmt? Notably it's pkgs.nixfmt-rfc-style in Nixpkgs.