[plt-scheme] (require... ) expanded from a macro

Hi,

I'm trying to port some of my software to PLT. I thought I could
emulate SRFI-55 using

(define-syntax require-extension
  (lambda (stx)
    (syntax-case stx (srfi)
      ((_ (srfi n))
       (with-syntax ((nstr (string-append
                                        (number->string
                                         (syntax-object->datum (syntax
n))) ".ss")))
         (syntax (require (lib nstr "srfi"))))))))

but it doesn't seem to work:

Language: Textual (MzScheme, includes R5RS).
> (require-extension (srfi 100))
;; it does look for a file
open-input-file: cannot open input file:
"/opt/plt/collects/srfi/100.ss" (No such file or directory; errno=2)
;; every is not pre-defined
> every
. reference to undefined identifier: every
;; seems to load without errors, but ...
> (require-extension (srfi 1))
> every
. reference to undefined identifier: every
> (require (lib "1.ss" "srfi"))
> every
#<procedure:every>
>

Aside from the surprising decision to exclude SRFI-0 and SRFI-55 from
PLT, why does this not work?

-- Dan Muresan