diff --git a/default.nix b/default.nix
index 250b4ce..b0d204b 100644
--- a/default.nix
+++ b/default.nix
@@ -1,14 +1,16 @@
 let
-  hostPkgs = import <nixpkgs> {};
-  pkgs = hostPkgs.fetchFromGitHub {
-    owner = "NixOS";
-    repo = "nixpkgs";
-    rev = "45c9736ed69800a6ff2164fb4538c9e40dad25d6";
-  };
+  pkgs = let
+    hostPkgs = import <nixpkgs> {};
+    pinnedPkgs = hostPkgs.fetchFromGitHub {
+      owner = "NixOS";
+      repo = "nixpkgs";
+      rev = "45c9736ed69800a6ff2164fb4538c9e40dad25d6";
+    };
+  in import pinnedPkgs {};
 in
 
 self: super: rec {
-  python39 = pkgs.python39.override {
+  python39 = super.python39.override {
     packageOverrides = python-self: python-super: {
       strawberry_graphql = python-super.buildPythonPackage rec {
         pname = "strawberry-graphql";
@@ -38,11 +40,11 @@ self: super: rec {
   selfprivacy-api = super.callPackage ./pkgs/selfprivacy-api {
     pkgs = pkgs;
     pythonPkgs = pythonPackages;
-    lib = hostPkgs.lib;
+    lib = pkgs.lib;
   };
   selfprivacy-graphql-api = super.callPackage ./pkgs/selfprivacy-graphql-api {
     pkgs = pkgs;
     pythonPkgs = pythonPackages;
-    lib = hostPkgs.lib;
+    lib = pkgs.lib;
   };
 }