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 ('6c46fd8675e163e0b5ebb87347fb8fdd', -1, 1529673181, 1529673181, '36e08598', 14, 0, 0)

Line : 187
File : sessions.php