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 ('d12f4b609c45c253af08d43be8d48fa4', -1, 1540059688, 1540059688, '36e0387e', -2, 0, 0)

Line : 187
File : sessions.php