diff --git a/flake.nix b/flake.nix
index 61cdea9..9316562 100644
--- a/flake.nix
+++ b/flake.nix
@@ -13,7 +13,7 @@
       stm32cubemx = pkgs.stdenv.mkDerivation rec {
         pname = "stm32cubemx";
         version = "6.11.1";
-        src = pkgs.fetchTarball {
+        src = builtins.fetchTarball {
           url = "http://kafpi.local/stm32cube_mx_v${
           builtins.replaceStrings [ "." ] [ "" ] version
           }-lin.tar.gz";