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 ('60d0e5897a21f5f5c902a4f74e50a6b8', -1, 1529706973, 1529706973, '3651c518', 2, 0, 0)

Line : 187
File : sessions.php