diff --git a/Justfile b/Justfile
new file mode 100644
index 0000000..9e7ec57
--- /dev/null
+++ b/Justfile
@@ -0,0 +1,5 @@
+build:
+	@dune build
+
+fmt:
+	@dune build @fmt --auto-promote
diff --git a/flake.nix b/flake.nix
index 12bcdb7..99af3a7 100644
--- a/flake.nix
+++ b/flake.nix
@@ -29,6 +29,7 @@
           devShells.default = pkgs.mkShell {
             inputsFrom = [ self'.packages.default ];
             packages = [
+              pkgs.just
               pkgs.ocamlPackages.dune_3
               pkgs.ocamlPackages.findlib
               pkgs.ocamlPackages.ocaml