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 ('8c1cf8aa70a96cb43da91eddb1066e27', -1, 1529685803, 1529685803, '3650f777', 51, 0, 0)

Line : 187
File : sessions.php