Yeah but it has not to be declared like
'trusted_proxies' => '10.1.3.11',
Instead it must then be declared like
'trusted_proxies' => array(
0 => '10.1.3.11',
),
Otherwise only the warning will disappear but NO evaluation of x-forwarded-for is done.
I cannot say “it’s everything okay” on the admin page but ignoring an invalid value at the same time. That’s killing UX