diff --git a/shell.nix b/shell.nix
index 4eb367f..00a07b7 100644
--- a/shell.nix
+++ b/shell.nix
@@ -2,6 +2,7 @@
   haskellPackages,
   haskell,
   zlib,
+  watchexec,
 }:
 haskellPackages.developPackage {
   name = "numbersquare";
@@ -11,8 +12,8 @@ haskellPackages.developPackage {
       addBuildTools =
         drv:
         haskell.lib.addBuildTools drv (
-          with haskellPackages;
-          [
+          [ watchexec ]
+          ++ (with haskellPackages; [
             fourmolu
             haskell-language-server
             cabal-install
@@ -20,7 +21,7 @@ haskellPackages.developPackage {
             ghcid
             cabal-fmt
             hoogle
-          ]
+          ])
         );
       addExtraLibraries = drv: haskell.lib.addExtraLibraries drv [ zlib ];
     in