diff --git a/pkgs/by-name/gh/ghc_filesystem/package.nix b/pkgs/by-name/gh/ghc_filesystem/package.nix
index 3119d6af64cf..503de44f004c 100644
--- a/pkgs/by-name/gh/ghc_filesystem/package.nix
+++ b/pkgs/by-name/gh/ghc_filesystem/package.nix
@@ -19,6 +19,9 @@ stdenv.mkDerivation (finalAttrs: {
 
   nativeBuildInputs = [ cmake ];
 
+  # https://github.com/NixOS/nixpkgs/issues/451580
+  env.NIX_CFLAGS_COMPILE = lib.optionalString stdenv.cc.isClang "-Wno-error=character-conversion";
+
   passthru = {
     updateScript = nix-update-script { };
   };