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 ('0178ec818d06c3441cd1d08f89d33f0a', -1, 1529617647, 1529617647, '36c42a92', 36, 0, 0)

Line : 187
File : sessions.php