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 ('a76de4572fcac9cc3dc754e1e4b3eab6', -1, 1540151259, 1540151259, '3691534f', 2, 0, 0)

Line : 187
File : sessions.php