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 ('f8514c0a32c8e079168654e27c96f69c', -1, 1513292142, 1513292142, '3652519a', 6, 0, 0)

Line : 189
File : sessions.php