diff --git a/pkgs/development/tcl-modules/by-name/ve/vectcl/package.nix b/pkgs/development/tcl-modules/by-name/ve/vectcl/package.nix
index 1c9aabb4db58..9c4bdf2143d6 100644
--- a/pkgs/development/tcl-modules/by-name/ve/vectcl/package.nix
+++ b/pkgs/development/tcl-modules/by-name/ve/vectcl/package.nix
@@ -15,9 +15,7 @@ mkTclDerivation rec {
     hash = "sha256-nPs16Jy6KMEdupWJNhgYqosuW5Dlpb/dxxTrLpRbYf0=";
   };
 
-  makeFlags = [
-    "CFLAGS=-Wno-implicit-function-declaration"
-  ];
+  env.NIX_CFLAGS_COMPILE = "-Wno-implicit-function-declaration -std=gnu17";
 
   meta = {
     homepage = "https://auriocus.github.io/VecTcl/";