For those who have the same problem:
This code works for both versions:
if (function_exists('acf_add_options_sub_page')) {
if( function_exists('acf_add_options_page') ) {
acf_add_options_page(); // necessary for v.5 :-/
}
acf_add_options_sub_page( 'standard' );
acf_add_options_sub_page( 'Wordpress Options' );
acf_add_options_sub_page( 'Settings' );
}