diff --git a/dev/flake.nix b/dev/flake.nix
index 7a3a4491..7637885d 100644
--- a/dev/flake.nix
+++ b/dev/flake.nix
@@ -14,6 +14,7 @@
       ];
       perSystem = { pkgs, lib, config, ... }: {
         treefmt = {
+          projectRoot = ../.;
           projectRootFile = "flake.nix";
           programs = {
             nixpkgs-fmt.enable = true;