diff --git a/pkgs/by-name/sa/sacc/package.nix b/pkgs/by-name/sa/sacc/package.nix
index 92907d8a110d..50599651c985 100644
--- a/pkgs/by-name/sa/sacc/package.nix
+++ b/pkgs/by-name/sa/sacc/package.nix
@@ -15,8 +15,8 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ ncurses libressl ];
 
-  CFLAGS = lib.optionals stdenv.hostPlatform.isDarwin [
-    "-D_DARWIN_C_SOURCE"
+  makeFlags = lib.optionals stdenv.hostPlatform.isDarwin [
+    "OSCFLAGS=-D_DARWIN_C_SOURCE"
   ];
 
   postPatch = ''