diff --git a/default.nix b/default.nix
index 12bc932..9cb4d12 100644
--- a/default.nix
+++ b/default.nix
@@ -1,5 +1,4 @@
-{ pkgs, lib ? pkgs.lib }: with lib;
-mapAttrs' (name: _: {
-  value = pkgs.python3.pkgs.callPackage (./python-pkgs/${name}) { };
-  name = removeSuffix ".nix" name;
-}) (builtins.readDir ./python-pkgs)
+{
+  pkgs ? (import <nixpkgs> { }),
+}:
+import pkgs.path { overlays = pkgs.overlays ++ [ (import ./overlay.nix) ]; }
diff --git a/overlay.nix b/overlay.nix
new file mode 100644
index 0000000..dd30998
--- /dev/null
+++ b/overlay.nix
@@ -0,0 +1,3 @@
+final: prev: with prev.lib; {
+  pythonPackagesExtensions = prev.pythonPackagesExtensions ++ [ import ./python_overlay.nix ];
+}
diff --git a/python_overlay.nix b/python_overlay.nix
new file mode 100644
index 0000000..3dc4b4f
--- /dev/null
+++ b/python_overlay.nix
@@ -0,0 +1,6 @@
+final: prev:
+with prev.lib;
+mapAttrs' (name: _: {
+  value = final.callPackage (./python-pkgs/${name}) { };
+  name = removeSuffix ".nix" name;
+}) (builtins.readDir ./python-pkgs)