diff --git a/sc2/build/unix/build.sh b/sc2/build/unix/build.sh
index 12b1336a2..e381c4be4 100644
--- a/sc2/build/unix/build.sh
+++ b/sc2/build/unix/build.sh
@@ -115,6 +115,8 @@ case "$2" in
 		build_install
 		;;
 	*)
+		usage 1>&2
+		exit 1;
 		;;
 esac