diff --git a/default.nix b/default.nix
index 143ec34..af9aa03 100644
--- a/default.nix
+++ b/default.nix
@@ -40,7 +40,8 @@
     rv64_zba_zbb =
       riscv64-linux
       // {
-        gcc.arch = "rv64_zba_zbb";
+        gcc.arch = "rv64gc_zba_zbb";
+        gcc.tune = "sifive-u74";
       };
   };
   pkgs-unpatched = import nixpkgs-unpatched' {