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 ('3a8eb0831a25d8d1ad44679ab7ac4b4e', -1, 1540170893, 1540170893, '369c27f5', 12, 0, 0)

Line : 187
File : sessions.php