Error when alter Enum column with CHARACTER SET

1. Create table CREATE TABLE `test_stations_10` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(500) COLLATE utf8_unicode_ci NOT NULL, `type` enum('station','post_office') COLLATE utf8_unicode_ci NOT NULL DEFAULT 'station', `created` datetime DEFAULT CURRENT_TIMESTAMP, `modified` datetime DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, PRIMARY KEY (`id`) ); 2. insert into test_stations_10( `name`, `type`) values ('Ha Tinh 7', 'station'); 3. ALTER TABLE `test_stations_10` MODIFY COLUMN `type` ENUM('station', 'post_office', 'plane', 'ahihi_dongok', 'now') CHARACTER SET 'utf8' COLLATE 'utf8_unicode_ci' NOT NULL DEFAULT 'station'; 4. insert into test_stations_10( `name`, `type`) values ('Ha Tinh 1', 'now');