Woocommerce - show coupon code & description in order email

//add coupon details in order email
add_action( 'woocommerce_email_after_order_table', 'wc89790_add_coupon_to_email', 20 );
function wc89790_add_coupon_to_email( $order ) {
    $coupons = $order->get_items('coupon');

    foreach ($coupons as $item_id => $item) {
        $coupon = new WC_Coupon( $item['name'] );
        $post = get_post($coupon->id);
        echo "<p class='coupon-used'><span class='coupon-name'><b>Coupon: " . $item['name'] . "</b></span></p>";
        echo "<p><span class='coupon-description'>" . $post->post_excerpt . "</span></p>";
    }
}