diff --git a/default.nix b/default.nix
index ad3f07f..de0dbe8 100644
--- a/default.nix
+++ b/default.nix
@@ -13,6 +13,7 @@ let
 in haskellEnv.overrideAttrs(o: {
   buildInputs = o.buildInputs ++
                 (with pkgs.elmPackages; [
+                  pkgs.entr
                   elm
                   elm-format
                   elm-optimize-level-2