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 ('5ff5c91704aebbc0c21a3ef2adea6b5a', -1, 1506313489, 1506313489, '36e0d65d', -8, 0, 0)

Line : 187
File : sessions.php