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 ('9fd705c5d7aaebc255d695a96aa662a3', -1, 1516784602, 1516784602, '36ea414e', 23, 0, 0)

Line : 189
File : sessions.php