diff --git a/.nix/fstar.nix b/.nix/fstar.nix
index 20785dfcfeb..49d1a6db252 100644
--- a/.nix/fstar.nix
+++ b/.nix/fstar.nix
@@ -13,6 +13,7 @@ stdenv.mkDerivation {
     "examples.*"
     "src(/ocaml-output(/Makefile)?)?"
     "ucontrib.*"
+    "mk.*"
   ];
 
   dontBuild = true;