[plt-scheme] Scope of eval?

What is wrong with this example?

Why isn't x in scope?

(require (lib "class.ss"))
(define example%
  (class* object% ()
    (define x 0)
    (define y "hello")
    (define/public (v-set name value)
      (eval `(set! ,name ,value)))
    (define/public (get-x) x)
    (define/public (get-y) y)
    (super-new)))

(define foo (new example%))
(send foo get-x)
(send foo v-set 'x 10)
=> error set!: cannot set undefined identifier: x