MySQL Error when upgrading from 7.6.4 to 7.6.5


I’m getting the following error while performing the upgrade to 7.6.5:

Thu Jul  7 13:27:48 2016 [8256][1][FATAL]  Query Failed: ALTER TABLE alerts   modify COLUMN subscribers varchar(65534)  NULL : MySQL error 1074: Column length too big for column 'subscribers' (max = 21845); use BLOB or TEXT instead

Server type: MySQL
Server version: 5.7.12-0ubuntu1 - (Ubuntu)
Server charset: UTF-8 Unicode (utf8)

PHP version:

I assume it has something to do with the encoding but I’m not sure what’s the best practice to go around this error. Any help is highly appreciated!