With MariaDB in a general case (backup, proper shutdown, storage engines incompatibilities, Galera, async replication, and maybe few bugs and corner cases aside) it should be possible to easily and directly upgrade from one major version to the other, skipping any number of intermediate major versions in between. mysql_upgrade utility is designed to fix all incompatibilities in the mysql.* system tables. In frames of this talk the details of its implementation and actions are discussed, as well as some known bugs and problems that it does not solve. Upgrades to MariaDB 10.4 and 10.5 are covered, from versions at least as old as MySQL 5.5.