diff --git a/contrib/cfssl.sh b/contrib/cfssl.sh
index 674a6932..17dd905e 100755
--- a/contrib/cfssl.sh
+++ b/contrib/cfssl.sh
@@ -8,6 +8,7 @@ srv_name="$2"
 [ -z "$srv_name" ] && {
 	echo "need arg 1: ca name"
 	echo "need arg 2: server name"
+	echo "optional arg 3: if set, write cert into copyparty cfg"
 	exit 1
 }