diff --git a/scripts/_common.sh b/scripts/_common.sh
index cac75a2..4596ed0 100644
--- a/scripts/_common.sh
+++ b/scripts/_common.sh
@@ -79,8 +79,8 @@ process_ips(){
             if [ "$(ynh_validate_ip4 --ip_address="$ip")" ] || [ "$(ynh_validate_ip6 --ip_address="$ip")" ] ; then
                 # don't process if the IP is public and the port 53 closed
                 if [ "$(is_public_ip "$ip")" == 0 ] && [ "$open_port_53" == "false" ] ; then
-                    # don't add this IP
-                    processed_ips+=""
+                    # don't add this IP (do nothing)
+                    :
                 else
                     processed_ips+="$ip "
                 fi