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 ('9fcfa39878c9794c1d2d79f8e9556eb2', -1, 1513292236, 1513292236, '3652519a', 2, 0, 0)

Line : 189
File : sessions.php