Ido and Vimpulse/Viper and C-p, C-n

Is there any way of getting C-p and C-n do ido-prev-match and ido-next-match in Ido mode? I’ve tried with the following, but it doesn’t work: (add-hook 'ido-setup-hook (lambda () (define-key ido-completion-map "\C-p" 'ido-prev-match) (define-key ido-completion-map "\C-n" 'ido-next-match) (viper-add-local-keys 'insert-state '(("\C-p" . ido-prev-match) ("\C-n" . ido-next-match)))))