diff --git a/default.nix b/default.nix
index 47df1c2..4a4ea5f 100644
--- a/default.nix
+++ b/default.nix
@@ -11,5 +11,6 @@
   '';
 
   # generates a script for running weeder
-  weeder-script = { local-packages, hs-pkgs }: import ./weeder-script.nix { inherit pkgs local-packages hs-pkgs; };
+  weeder-script = { local-packages, hs-pkgs, weeder ? pkgs.haskellPackages.weeder }:
+    import ./weeder-script.nix { inherit pkgs weeder local-packages hs-pkgs; };
 }
diff --git a/weeder-script.nix b/weeder-script.nix
index 8d8e6f5..8556a68 100644
--- a/weeder-script.nix
+++ b/weeder-script.nix
@@ -1,6 +1,7 @@
 { pkgs,  # nixpkgs package set
   local-packages,  # list of local haskell packages in the project and their subdirectories
-  hs-pkgs  # package set returned by `haskell-nix.stackProject`
+  hs-pkgs,  # package set returned by `haskell-nix.stackProject`
+  weeder  # weeder package
 }:
 
 with rec {
@@ -56,7 +57,7 @@ with rec {
     export PATH="${fake-stack}/bin:$PATH"
 
     # run weeder
-    ${pkgs.haskellPackages.weeder}/bin/weeder stack.yaml --dist dist-hi
+    ${weeder}/bin/weeder stack.yaml --dist dist-hi
   '';
 };