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, session_admin) VALUES ('a4c09d85fa9d893b7fa2bdb2b71cc7ed', -1, 1216995905, 1216995905, '26673f11', 26, 0, 0)

Line : 187
File : sessions.php