Error message after upgrade

[Rici]

Just tried to upgrade my old ipb3.4 in a test environment: no chance to get it running locally so I had to create a backup version on my webspace.

Upgrade process went through (not without problems...) but now after installation I get this message when trying to login in the acp:

Fatal error: Uncaught exception 'IPS\Db\Exception' with message 'Column 'session_log_in_time' cannot be null' in /www/htdocs/*****/system/Db/Db.php:398 Stack trace: #0 /www/htdocs/*****/system/Db/Db.php(631): IPS\_Db->preparedQuery('REPLACE INTO `c...', Array) #1 /www/htdocs/*****/system/Session/Admin.php(115): IPS\_Db->replace('core_sys_cp_ses...', Array) #2 [internal function]: IPS\Session\_Admin->write('ab45ae762776d80...', '') #3 {main} thrown in /www/htdocs/*****/system/Db/Db.php on line 398

Any ideas what happened here?

[Prank]

Me too, any tips?