[plt-scheme] Macros and quasi-quotation

I accidently ran across billiard.scm posted to
comp.lang.scheme by Morris Katz the 21'st of may 1989
and tried to run it.

Mzscheme refused due to the use af define-macro. Here
is a distilled example:

  > (define-macro (a) 1)
  > (define-macro (b) (a))
  > (b)
  . reference to undefined identifier: a
  > (a)
  1

Is this intensional?

(It runs in bigloo and scm.)

--
Jens Axel Søgaard