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 ('eb33e2e56bb8fd5a11a95261b7bee7a4', -1, 1540141956, 1540141956, '36e0387e', -4, 0, 0)

Line : 187
File : sessions.php