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 ('29a65edd79412fa903399b8b81b1a181', -1, 1513622088, 1513622088, '3652385f', -4, 0, 0)

Line : 193
File : sessions.php