phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in) VALUES ('71f3e15dc99552449a57171a53febd31', -1, 1397984094, 1397984094, '36e278b7', 14, 0)

Line : 158
File : sessions.php