MySQL key length issue again

[kinnalru]

$ vines schema wonderland.lit
-- create_table(:users, {:force=>false})
-> 0.1843s
-- add_index(:users, :jid, {:unique=>true})
Schema creation failed: Mysql2::Error: Specified key was too long; max key length is 767 bytes: CREATE UNIQUE INDEX index_users_on_jid ON users (jid)

$ gem list vines

*** LOCAL GEMS ***

vines (0.4.7)
vines-agent (0.1.4)
vines-couchdb (0.1.0)
vines-services (0.1.4)
vines-sql (0.1.0)
vines-web (0.1.1)

[kinnalru]

storage 'sql' do
  adapter 'mysql2'
  host 'localhost'
  port 5432
  database 'xmpp'
  username 'root'
  password ''
  pool 5
end