Archive widget – limit number of months to 12

The default Archive widget display monthly archives in a dropdown.

I would like to limit the number of months to 12 (in dropdown).

What filter I should apply in my functions.php?

I tried this, but it gives me parsed error:

add_filter('WP_Widget_Archives','set_number_months');
function set_number_months($args) {
$args = array('number'    => 12);
return $args;
}

I also tried with wp_get_archives but same parsed error

Use the widget_archives_args filter to add the archives limit.

function my_limit_archives( $args ) {
    $args['limit'] = 12;
    return $args;
}
add_filter( 'widget_archives_args', 'my_limit_archives' );

And to limit the number of months in Archives widget dropdown use the following drop down filter.

add_filter( 'widget_archives_dropdown_args', 'my_limit_archives' );