redeclare class condition_info

I upgrade my moodle from 2.6.4 to 2.7.1. After upgrading I've got blank (white) screen. Then I turn on debug display in config.php $CFG->debug = 32767; $CFG->debugdisplay = true; After that I receive an error: Fatal error: Cannot redeclare class condition_info in /home/moodle/public_html/lib/conditionlib.php on line 105. Then I search and found that might be a problem with opcache (https://tracker.moodle.org/browse/MDL-45797). So I follow this doc - http://docs.moodle.org/27/en/admin/environment/php_setting/opcache.enable and enable opcache in php.ini: [opcache] opcache.enable = 1 opcache.memory_consumption = 128 opcache.max_accelerated_files = 4000 opcache.revalidate_freq = 60 ; Required for Moodle opcache.use_cwd = 1 opcache.validate_timestamps = 1 opcache.save_comments = 1 opcache.enable_file_override = 0 ; If something does not work in Moodle ;opcache.revalidate_path = 1 ; May fix problems with include paths ;opcache.mmap_base = 0x20000000 ; (Windows only) fix OPcache crashes with event id 487 ; Experimental for Moodle 2.6 and later ;opcache.fast_shutdown = 1 ;opcache.enable_cli = 1 ; Speeds up CLI cron ;opcache.load_comments = 0 ; May lower memory use, might not be compatible with add-ons and other apps. Reload apache and it still doesn't work. I also try to comment out part *; If something does not work in Moodle* and error still occurs. Any idea what might be wrong? I also read that might be a problem with themes. Before I upgrade I switch theme to Clean which is default theme in 2.7. I have ubuntu 14.04 with PHP 5.5.9-1ubuntu4.3 (cli) (built: Jul 7 2014 16:36:58)