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 ('641479be000ef1a3214a6b87e9e648d7', -1, 1544565536, 1544565536, '36e31f91', 3, 0, 0)

Line : 187
File : sessions.php