mysql/mariadb - create table column index not working

So I'm trying to create my table as follows:

CREATE TABLE company
  (
    id INT UNSIGNED PRIMARY KEY NOT NULL AUTO_INCREMENT,
    name TEXT UNIQUE NOT NULL,

    INDEX(name(20))
  );

It's giving me this error:

ERROR 1170 (42000): BLOB/TEXT column 'name' used in key specification without a key length

I'm not sure why it's not working as I'm following the guide here: https://dev.mysql.com/doc/refman/5.5/en/column-indexes.html