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 ('515cb6e0a33ed0b486544751bddbe7b8', -1, 1529939417, 1529939417, '36e0ebb7', -4, 0, 0)

Line : 172
File : sessions.php