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 ('7e2b66f5b6a63b53f47bc95fb49f2042', -1, 1540252371, 1540252371, '369ed0bd', 5, 0, 0)

Line : 187
File : sessions.php