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 ('bfa393ad1067e7a6b7ebaa95c1ed3bbb', -1, 1529760833, 1529760833, '36e0ebb7', 17, 0, 0)

Line : 187
File : sessions.php