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 ('a6dc0f6ea2b1d57d85a95a1d05f40bed', -1, 1571335143, 1571335143, '12cc3028', 28, 0, 0)

Line : 191
File : sessions.php