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 ('3d077dc86dd22dc41bbda41c12b64313', -1, 1484599846, 1484599846, '36cd2f1a', 0, 0, 0)

Line : 189
File : sessions.php