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 ('2d5b0d7f8a0ae0d35e589ad23f27bf16', -1, 1513239169, 1513239169, '365bab89', 20, 0, 0)

Line : 192
File : sessions.php