When I tried to update the database from phpBB 3.0.11 to the current state on the repo, he threw a fatal error:

Call to a member function get_finder() on a non-object in includes/acp/acp_modules.php at line 554

Solution is renaming $extension_manager to $phpbb_extension_manager in install/database_update.php at line 216 (and 217 too).