Using custom error messages for nested attributes in Laravel validator

I am validating a nested attribute in Laravel (5.2)

$this->validate($request, [
    'title' => 'required',
    'author.name' => 'required',
    'author.description' => 'required',
]);

In my custom validation language file title works, but author.name and author.description don't work.

'custom' => [
    'title' => [
        'required' => 'The title is required',
    ],
    'author.name' => [
        'required' => 'Name is required',
    ],
    'author.description' => [
        'required' => 'Description is required',
    ],
],

via Chebli Mohamed