diff --git a/flake.nix b/flake.nix
index 1b1e698..5958e06 100644
--- a/flake.nix
+++ b/flake.nix
@@ -43,6 +43,7 @@
                 export GHC_PACKAGE_PATH="dist/package.conf.inplace:$GHC_PACKAGE_PATH"
               '';
             });
+            fourmolu = pkgs.haskell.packages.ghc944.fourmolu;
           };
         };