diff --git a/nix/agda2hs.nix b/nix/agda2hs.nix
index b13c3767..216bdefa 100644
--- a/nix/agda2hs.nix
+++ b/nix/agda2hs.nix
@@ -1,47 +1,32 @@
-
-{
-  stdenv,
-  lib,
-  self,
-  agda2hs,
-  runCommandNoCC,
-  makeWrapper,
-  writeText,
-  mkShell,
-  ghcWithPackages,
-}:
+# this file should be very close to a copy of nixpkgs/pkgs/build-support/agda/default.nix
+# I think I took the version from https://github.com/NixOS/nixpkgs/blob/bbe6402ecacfc3a0e2c65e3527c2cbe148b98ff8/pkgs/build-support/agda/default.nix
+# but it would be nice to expose this in upstream so that we don't have to duplicate the file
+{stdenv, lib, self, agda2hs, runCommandNoCC, makeWrapper, writeText, mkShell, ghcWithPackages}:
 with lib.strings;
 let
-  withPackages' =
-    {
+  withPackages' = {
       pkgs,
-      ghc ? ghcWithPackages (p: with p; [ ieee754 ]),
-    }:
-    let
-      pkgs' = if builtins.isList pkgs then pkgs else pkgs self;
-      library-file = writeText "libraries" ''
-        ${(concatMapStringsSep "\n" (p: "${p}/${p.libraryFile}") pkgs')}
-      '';
-      pname = "agda2hsWithPackages";
-      version = agda2hs.version;
-    in
-    runCommandNoCC "${pname}-${version}"
-      {
-        inherit pname version;
-        nativeBuildInputs = [ makeWrapper ];
-        passthru.unwrapped = agda2hs;
-      }
-      ''
-        mkdir -p $out/bin
-        makeWrapper ${agda2hs}/bin/agda2hs $out/bin/agda2hs \
-          --add-flags "--with-compiler=${ghc}/bin/ghc" \
-          --add-flags "--library-file=${library-file}" \
-          --add-flags "--local-interfaces"
-      ''; # Local interfaces has been added for now: See https://github.com/agda/agda/issues/4526
-  withPackages =
-    arg: if builtins.isAttrs arg then withPackages' arg else withPackages' { pkgs = arg; };
-in
-{
+      ghc ? ghcWithPackages (p: with p; [ ieee754 ])
+  }: let
+    pkgs' = if builtins.isList pkgs then pkgs else pkgs self;
+    library-file = writeText "libraries" ''
+      ${(concatMapStringsSep "\n" (p: "${p}/${p.libraryFile}") pkgs')}
+    '';
+    pname = "agda2hsWithPackages";
+    version = agda2hs.version;
+  in runCommandNoCC "${pname}-${version}" {
+    inherit pname version;
+    nativeBuildInputs = [ makeWrapper ];
+    passthru.unwrapped = agda2hs;
+  } ''
+    mkdir -p $out/bin
+    makeWrapper ${agda2hs}/bin/agda2hs $out/bin/agda2hs \
+      --add-flags "--with-compiler=${ghc}/bin/ghc" \
+      --add-flags "--library-file=${library-file}" \
+      --add-flags "--local-interfaces"
+    ''; # Local interfaces has been added for now: See https://github.com/agda/agda/issues/4526
+  withPackages = arg: if builtins.isAttrs arg then withPackages' arg else withPackages' { pkgs = arg; };
+in {
   inherit withPackages;
-  agda2hs = withPackages [ ];
+  agda2hs = withPackages [];
 }