diff --git a/flake.nix b/flake.nix
index af855a9..5801376 100644
--- a/flake.nix
+++ b/flake.nix
@@ -36,7 +36,7 @@
         inherit system;
         config = { };
         overlays = builtins.attrValues self.overlays ++ [
-          (prev: final: import ./nix/protobuf.nix {pkgs = prev;})
+          (prev: final: import ./nix/protobuf.nix final)
           (prev: final: {
               # This plugin path won't work because it's relative to the pwd
               protoc-gen-purescript = prev.writeScriptBin "protoc-gen-purescript" ''
diff --git a/nix/protobuf.nix b/nix/protobuf.nix
index d50faeb..37e33fe 100644
--- a/nix/protobuf.nix
+++ b/nix/protobuf.nix
@@ -1,4 +1,5 @@
-{ pkgs ? import <nixpkgs> { } }:
+{ stdenv, lib, fetchFromGitHub, autogen, automake, autoconf, libtool, rsync, cmake, ... }:
+# pkgs ? import <nixpkgs> { } }:
 
 # The protobuf derivation in nixpkgs does not include the conformance test
 # runners.
@@ -66,7 +67,7 @@ let
   };
   protobuf_repo_v23_2 = rec {
     ref = "v23.2";
-    src = pkgs.fetchFromGitHub {
+    src = fetchFromGitHub {
       owner = "protocolbuffers";
       repo = "protobuf";
       rev = "v23.2";
@@ -76,7 +77,7 @@ let
   };
   protobuf_repo_v24_4 = rec {
     ref = "v24.4";
-    src = pkgs.fetchFromGitHub {
+    src = fetchFromGitHub {
       owner = "protocolbuffers";
       repo = "protobuf";
       rev = "v24.4";
@@ -86,7 +87,7 @@ let
   };
   protobuf_repo_v28_2= rec {
     ref = "v28.2";
-    src = pkgs.fetchFromGitHub {
+    src = fetchFromGitHub {
       owner = "protocolbuffers";
       repo = "protobuf";
       rev = "v28.2";
@@ -104,9 +105,9 @@ let
   #
   # See the Travis test runner script
   # https://github.com/protocolbuffers/protobuf/blob/master/tests.sh
-  mkProtobuf = repo: pkgs.stdenv.mkDerivation {
+  mkProtobuf = repo: stdenv.mkDerivation {
     name = "protobuf-${repo.ref}";
-    nativeBuildInputs = with pkgs; [ autogen automake autoconf libtool rsync ];
+    nativeBuildInputs = [ autogen automake autoconf libtool rsync ];
     src = repo.src;
     # https://github.com/protocolbuffers/protobuf/blob/main/src/README.md#c-installation---unix
     configurePhase = ''
@@ -139,21 +140,21 @@ let
         and conformance .proto definitions.
         '';
       homepage = "https://github.com/xc-jp/purescript-protobuf";
-      license = pkgs.lib.licenses.bsd3;
+      license = lib.licenses.bsd3;
       mainProgram = "protoc";
     };
   };
 
-  cmakeProtobuf = repo: pkgs.stdenv.mkDerivation {
+  cmakeProtobuf = repo: stdenv.mkDerivation {
     name = "protobuf-${repo.ref}";
-    nativeBuildInputs = with pkgs; [ cmake rsync ];
+    nativeBuildInputs = [ cmake rsync ];
     src = repo.src;
     # https://github.com/protocolbuffers/protobuf/blob/main/src/README.md#c-installation---unix
     cmakeFlags = [ "-Dprotobuf_BUILD_CONFORMANCE=ON" ];
     postInstall =
       let
-        conformance_rpath = pkgs.lib.makeLibraryPath [
-          pkgs.stdenv.cc.cc.lib
+        conformance_rpath = lib.makeLibraryPath [
+          stdenv.cc.cc.lib
         ];
       in
       ''
@@ -165,11 +166,11 @@ let
       # Conformance test runner
       cp ./conformance_test_runner $out/bin/conformance_test_runner
       # https://nixos.wiki/wiki/Packaging/Binaries#Creating_the_Derivation_for_upstream_Packaging
-      patchelf --set-interpreter "${pkgs.stdenv.cc.bintools.dynamicLinker}" --set-rpath "$out/lib:${conformance_rpath}" $out/bin/conformance_test_runner
+      patchelf --set-interpreter "${stdenv.cc.bintools.dynamicLinker}" --set-rpath "$out/lib:${conformance_rpath}" $out/bin/conformance_test_runner
 
       # Distribute the cpp conformance program as a test case
       cp ./conformance_cpp $out/bin/conformance_cpp
-      patchelf --set-interpreter "${pkgs.stdenv.cc.bintools.dynamicLinker}" --set-rpath "$out/lib:${conformance_rpath}" $out/bin/conformance_cpp
+      patchelf --set-interpreter "${stdenv.cc.bintools.dynamicLinker}" --set-rpath "$out/lib:${conformance_rpath}" $out/bin/conformance_cpp
       '';
     meta = {
       description = "Google’s Protobuf built for purescript-protobuf";
@@ -179,7 +180,7 @@ let
         and conformance .proto definitions.
         '';
       homepage = "https://github.com/xc-jp/purescript-protobuf";
-      license = pkgs.lib.licenses.bsd3;
+      license = lib.licenses.bsd3;
       mainProgram = "protoc";
     };
   };