Mysql database bug

Please change lengths 256 to 255, with 256, primary key creation raise arror and mysql dont work:

mysql> CREATE TABLE sharejs.snapshots (
-> doc varchar(256) NOT NULL,
-> v int NOT NULL,
-> type varchar(256) NOT NULL,
-> snapshot text NOT NULL,
-> meta text NOT NULL,
-> created_at timestamp NOT NULL,
-> CONSTRAINT snapshots_pkey PRIMARY KEY (doc, v)
-> )
-> ;
ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes