MySQL: ERROR 1045 (28000) when GRANT

Description

# mysql -uroot -p123456
mysql> GRANT ALL PRIVILEGES ON *.* TO 'xyzuser'@'localhost' IDENTIFIED BY 'xyzuser'  WITH GRANT OPTION;
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

# mysql_upgrade -uroot -p123456

# mysql -uroot -p123456
mysql> GRANT ALL PRIVILEGES ON *.* TO 'xyzuser'@'localhost' IDENTIFIED BY 'xyzuser'  WITH GRANT OPTION;
Query OK, 0 rows affected (0.00 sec)