mysql_upgrade で FATAL ERROR

FreeBSD の pkg で MySQL を 5.5 から 5.6 へアップグレードして、mysql_upgrade したら、FATAL ERROR が出た。

mysql_upgrade -u root -p

でok

Message for mysql56-server-5.6.23:
************************************************************************
Remember to run mysql_upgrade the first time you start the MySQL server
after an upgrade from an earlier version.

************************************************************************
root@hoge:/usr/pub/Backup # mysql_upgrade
Looking for 'mysql' as: mysql
Looking for 'mysqlcheck' as: mysqlcheck
FATAL ERROR: Upgrade failed
root@hoge:/usr/pub/Backup # service mysql-server start
Starting mysql.
root@hoge:/usr/pub/Backup # mysql_upgrade
Looking for 'mysql' as: mysql
Looking for 'mysqlcheck' as: mysqlcheck
FATAL ERROR: Upgrade failed
root@hoge:/usr/pub/Backup # mysql_upgrade -u root -p
Enter password:
Looking for 'mysql' as: mysql
Looking for 'mysqlcheck' as: mysqlcheck
Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/tmp/mysql.sock'
(以下略)