WooCommerce won't allow me to set a custom order status

I’ve used the following code to add a couple new order statuses to WooCommerce:

// Register new status
function register_woocommerce_status() {
    register_post_status( 'wc-ready-for-pickup', array(
        'label'                     => 'Ready for Pickup',
        'public'                    => true,
        'exclude_from_search'       => false,
        'show_in_admin_all_list'    => true,
        'show_in_admin_status_list' => true,
        'label_count'               => _n_noop( 'Ready for Pickup (%s)', 'Ready for Pickup (%s)' )
    ) );

    register_post_status( 'wc-ready-for-delivery', array(
        'label'                     => 'Ready for Delivery',
        'public'                    => true,
        'exclude_from_search'       => false,
        'show_in_admin_all_list'    => true,
        'show_in_admin_status_list' => true,
        'label_count'               => _n_noop( 'Ready for Delivery (%s)', 'Ready for Delivery (%s)'     )
    ) );
}
add_action( 'init', 'register_woocommerce_status' );    

// Add to list of WC Order statuses
function add_awaiting_shipment_to_order_statuses( $order_statuses ) {

    $new_order_statuses = array();

    // add new order status after processing
    foreach ( $order_statuses as $key => $status ) {

        $new_order_statuses[ $key ] = $status;

        if ( 'wc-processing' === $key ) {
            $new_order_statuses['wc-ready-for-pickup'] = 'Ready for Pickup';
            $new_order_statuses['wc-ready-for-delivery'] = 'Ready for Delivery';
        }
    }

    return $new_order_statuses;
}
add_filter( 'wc_order_statuses', 'add_awaiting_shipment_to_order_statuses' );

This all works great for “Ready for Pickup”, but if I try to set the order status to “Ready for Delivery” it just simply won’t reset. It adds to the order notes saying that it did so, but it doesn’t actually set it.

Any ideas what the issue is?