phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('bb3755e2a1cf489d5133eadd491d78f0', -1, 1417237146, 1417237146, '365a42ed', 4, 0, 0)

Line : 187
File : sessions.php