diff --git a/install.sh b/install.sh
index cc2fef5e6e3e13e1cfa29fd0cc8d2045829e5689..cdf85a1115b019c5d55e8c2e0d0ba3e9d9da06d6 100755
--- a/install.sh
+++ b/install.sh
@@ -99,6 +99,8 @@ for arg in "$@"; do
             BUILD=true;GTEST=true ;;
         -j* )
             J="${arg//-j=/}" ;;
+        * )
+            usage ;;
     esac
 done