diff --git a/artiq-fast/pkgs/llvm-or1k.nix b/artiq-fast/pkgs/llvm-or1k.nix
index b305485..fc6925e 100644
--- a/artiq-fast/pkgs/llvm-or1k.nix
+++ b/artiq-fast/pkgs/llvm-or1k.nix
@@ -33,8 +33,6 @@ in
     buildInputs = [ perl groff cmake libxml2 python libffi ] ++ stdenv.lib.optional stdenv.isLinux valgrind;
 
     preBuild = ''
-      NIX_BUILD_CORES=4
-      makeFlagsArray=(-j''$NIX_BUILD_CORES)
       mkdir -p $out/
     '';