Thread:Project:Support desk/Upgrade = Call to undefined method Title::userCanRead()

My upgrade to 1.25 seemed to work, but in fact not. Here is the last error message: -- Fatal error: Call to undefined method Title::userCanRead in [...]/includes/Wiki.php on line 158 --

It might have something to do with a missing extension, for I removed a lot of them to simplify first.

Thanks in advance for any hint.