[racket] Getting unusual behavior from racket/sandbox: not truly capping memory usage?!

Test case:

###################################
#lang racket

(define ip (open-input-string "hello world"))
(define evt (peek-bytes-evt 1 0 #f ip))
(let loop ()
  (sync (handle-evt evt
                    (lambda (res)
                      (loop)))))
###################################

If I'm reading 'top' correctly, this shows the memory leak.