Problem when saving IPs

Hello, there’s a problem on my site when saving ip addresses.
I write the ip addresses one per line, and after saving only the first address is visible in the textarea, the other get lost.
Looking in the database (wp_options table) I see the option secure_admin_ip_list is saved (xxx.xxx.xxx.xxx\nyyy.yyy.yyy.yyy) but the whitelist works only for the first ip