diff --git a/NT/tools/ar b/NT/tools/ar
index f94ed14e134a1da6ad76c389a0b77a387d409dc6..95c9b09b932c34f7753ce3c7b7e8f8423bb87603 100755
--- a/NT/tools/ar
+++ b/NT/tools/ar
@@ -109,6 +109,7 @@ case "$CC" in
   ;;
   *)
     echo Unknown C compiler: $CC
+    exit 1
   ;;
 esac