phpBB : Critical Error

Error doing DB query userdata row fetch

DEBUG MODE

SQL Error : 2006 MySQL server has gone away

SELECT u.*, s.* FROM phpbb_sessions s, phpbb_users u WHERE s.session_id = 'd9b3b79941b9f2fcb3574eb60f7a7ad8' AND u.user_id = s.session_user_id

Line : 267
File : sessions.php