diff --git a/flake.nix b/flake.nix
index a11835b..6c622e4 100644
--- a/flake.nix
+++ b/flake.nix
@@ -13,6 +13,7 @@
       {
         devShells.default = pkgs.mkShell {
           packages = with pkgs; [
+            d2 # to format .d2 files
             wd2.packages.${system}.default
             deno
             nodejs-18_x