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 ('961a40ea8f65f9e0bd90b1d7ab1b24c7', -1, 1566115548, 1566115548, '12e835e7', -9, 0, 0)

Line : 187
File : sessions.php