[racket] strange behaviour of a (match) form

Hi, all

Accidentally, I found out that null matchs in unexpected way (seems it
matchs always)

So,
(define (length-my list)
  (match list
    ['() 0]
    [(cons x xs)
     (+ 1
        (length-my xs))]
    [_ 'not-a-list]))
(length-my '(1 2 3 4))
>produces 4

But
(define (length-my list)
  (match list
    [null 0]
    [(cons x xs)
     (+ 1
        (length-my xs))]
    [_ 'not-a-list]))
(length-my '(1 2 3 4))
>produces 0

I also tried that:
(match '213423
  [null 0]
  [_ 1])
>produces 0
(match null
  ['213423 0]
  [_ 1])
>produces 1

Is it a bug?

I am using Racket 6.1

-- 
Best regards,
Yuri
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.racket-lang.org/users/archive/attachments/20141002/adbadaf0/attachment.html>