diff --git a/pkgs/by-name/li/libossp_uuid/package.nix b/pkgs/by-name/li/libossp_uuid/package.nix
index a04339778f05..57078f4741eb 100644
--- a/pkgs/by-name/li/libossp_uuid/package.nix
+++ b/pkgs/by-name/li/libossp_uuid/package.nix
@@ -14,7 +14,7 @@ stdenv.mkDerivation rec {
   };
 
   configureFlags = [
-    "ac_cv_va_copy=yes"
+    "ac_cv_va_copy=C99"
   ] ++ lib.optional stdenv.hostPlatform.isFreeBSD "--with-pic";
 
   patches = [ ./shtool.patch ];