diff --git a/pkgs/by-name/at/ats2/package.nix b/pkgs/by-name/at/ats2/package.nix
index 339d9e6b7e31..dfe6fe406525 100644
--- a/pkgs/by-name/at/ats2/package.nix
+++ b/pkgs/by-name/at/ats2/package.nix
@@ -52,7 +52,7 @@ stdenv.mkDerivation rec {
     "CCOMP=${stdenv.cc.targetPrefix}cc"
   ];
 
-  env.NIX_CFLAGS_COMPILE = lib.optionalString stdenv.cc.isClang "-Wno-error=implicit-function-declaration";
+  env.NIX_CFLAGS_COMPILE = "-Wno-error=implicit-function-declaration";
 
   setupHook =
     let