phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('879f63f2658a99712be524489058a34b', -1, 1539804743, 1539804743, '36a6cfdf', 6, 0, 0)

Line : 187
File : sessions.php