phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('f65f97a300018b55c6e0c76f4ce66894', -1, 1540286705, 1540286705, '36a174e1', -8, 0, 0)

Line : 187
File : sessions.php