Socks5 password authentication not working

configured relay with

Socks5ProxyUsername user Socks5ProxyPassword pass

added to FF 'prefs.js'

user_pref("network.proxy.socks_username", "user"); user_pref("network.proxy.socks_password", "pass");

not working as far as I can tell

Wireshark of connection shows

Socks Protocol Version: 5 Client Authentication Methods Authentication Method Count: 1 Method[0]: 0 (No authentication)

so relay is not enforcing authentication and I don't see any options for requiring that it do so