version control with tramp problem

[Vektor]

I have backup version control config like these:

;; backup version control
(setq version-control t)
(setq kept-new-versions 3)
(setq delete-old-versions t)
(setq kept-old-versions 2)
(setq dired-kept-versions 1)
(setq backup-directory-alist '(("" . "~/Document/backup/emacsed")))

But when I edit files through tramp as other users, such as root.
There still will be backup files like xxx.~1~. Why? And how to get rid
of them?
-- 
Remove all XYZ from my email to get the real one.