Hide metabox for specific role

Hi,

I need to hide the metabox from "Edit page" when the role "Author" is editing a page.

I have tried the following solutions:

add_action( 'add_meta_boxes' );

if (is_admin()) :
	function remove_plugin_metaboxes(){
		if ( ! current_user_can( 'author' ) ) {
			remove_meta_box('customsidebars-mb', 'page', 'normal');
		}
	}
	add_action( 'do_meta_boxes', 'remove_plugin_metaboxes' );
endif;
//and this:
if (is_admin()) :
	function remove_page_meta_boxes() {
			if(current_user_can('author')) {
			remove_meta_box('customsidebars-mb', 'page', 'normal');
		}
	}
	add_action( 'admin_menu', 'remove_page_meta_boxes' );
endif;

However, both of them removes your customisation of the metabox, but leaves the standard Sidebars metabox to be shown.

If I disable your plugin I can easily hide the Sidebars metabox.

Do you know how to solve this?