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 ('94e8bb7c7aab94412a1e3c611118146b', -1, 1529707327, 1529707327, '3651c518', -9, 0, 0)

Line : 187
File : sessions.php