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 ('6c37a563f4877d1cece066c6a4c171ad', -1, 1488065287, 1488065287, '3691cdb2', 8, 0, 0)

Line : 187
File : sessions.php