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 ('ee7192213cd5e3dc4af41e54d6824696', -1, 1513438499, 1513438499, '365bab89', 0, 0, 0)

Line : 187
File : sessions.php