TeleTet : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('d2e35c71cc2ab3f8c2bc0e38c4ee9cd2', -1, 1413981127, 1413981127, '36a79004', -16, 0, 0)

Line : 189
File : sessions.php