diff --git a/Dothem b/Dothem
index 38a37f2ba4..a27f221c3f 100755
--- a/Dothem
+++ b/Dothem
@@ -14,6 +14,7 @@ while	case "$1" in
 	--base=*) BUILDBASE=${1#*=} ;;
 	--branches=*) branches=${1#*=} ;;
 	-j*) jobs=$1 ;;
+	-*) echo >&2 "Unknown option: $1"; exit 1 ;;
 	*) break ;;
 	esac
 do