diff --git a/byg/default.nix b/byg/default.nix
index 541d5d7..86e58f0 100644
--- a/byg/default.nix
+++ b/byg/default.nix
@@ -1,2 +1,9 @@
 with import ./nix/common.nix;
-haskell.callCabal2nix "byg" ./. { }
+pkgs.haskell.lib.overrideCabal
+  (haskell.callCabal2nix "byg" ./. { })
+  (_: {
+    configureFlags = [
+      "--ghc-option=-Werror"
+      "--ghc-option=-O2"
+    ];
+  })