diff --git a/default.nix b/default.nix
index 344d9da..b83bd38 100644
--- a/default.nix
+++ b/default.nix
@@ -11,7 +11,7 @@ let
 in
 
 self: super: rec {
-  python39 = super.python39.override {
+  python39 = pkgs.python39.override {
     packageOverrides = python-self: python-super: {
       strawberry_graphql = python-super.buildPythonPackage rec {
         pname = "strawberry-graphql";