NC20 isn't respecting 'X-Forwarded-For' header from reverse proxy

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