diff --git a/plugins/network/ipset b/plugins/network/ipset
index c7bb0a3a..b777351f 100755
--- a/plugins/network/ipset
+++ b/plugins/network/ipset
@@ -45,13 +45,15 @@ GPLv2
 
 =cut
 
+set -eu
+
 
 get_ipset_list() {
 	ipset list -n
 }
 
 
-if [ "$1" = "autoconf" ]; then
+if [ "${1:-}" = "autoconf" ]; then
 	if [ -e /sbin/ipset ] || [ -n "$(which ipset)" ]; then
 		echo 'yes'
 	else
@@ -60,7 +62,7 @@ if [ "$1" = "autoconf" ]; then
 	exit 0
 fi
 
-if [ "$1" = "config" ]; then
+if [ "${1:-}" = "config" ]; then
 	echo graph_title Netfilter IPSets
 	echo graph_category network
 	echo graph_vlabel Members