phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO zagataphpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('8f4bca483fc5df6e59fa5368f16cfd0a', -1, 1484934984, 1484934984, 'ae81789b', 8, 0, 0)

Line : 187
File : sessions.php