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 ('8962a72892a5d54534d51d5a4041cdf8', -1, 1409640099, 1409640099, '36e2124a', 9, 0, 0)

Line : 172
File : sessions.php