Thread:Extension talk:WPMW/Fatal error: Unknown: Cannot use output buffering in output buffering display handlers in Unknown on line 0

Trying to install this with WordPress 4.1.1. Installed MediaWiki on /wiki, everything else (.htaccess and .php settings) seems ok, but I get this message: Fatal error: Unknown: Cannot use output buffering in output buffering display handlers in Unknown on line 0.

Any suggestions?