Order archive by meta #wordpress

archive-meta-sort.php

/**
 * Order person achive results A-Z by last name
 */
function baindesign324_reorder_posts_person( $query ) {
    if( isset($query->query_vars['post_type']) && $query->query_vars['post_type'] == 'cpt1' ) {          
        $query->set('orderby', 'meta_value');	
        $query->set('meta_key', 'last_name');	 
        $query->set('order', 'ASC');
    }
}
add_action( 'pre_get_posts', 'baindesign324_reorder_posts_person' );