Failure to modify Moo::Role attribute from Moose class

gistfile1.pl

use strict;
use warnings;

{

    package MyClass;
    use Moose;

    with 'Role::REST::Client';

    has '+server' => (
        lazy    => 1,
        builder => '_build_server',
    );

    sub _build_server {
        'foo';
    }
}


my $o = MyClass->new();

"Must have an is at .../Method/Generate/Accessor.pm line 47"