How to use the simple-macros egg?

For instructions on how to use the simple-macros implementation,
http://www.call-with-current-continuation.org/eggs/simple-macros.html
says merely:

> Usage:
> (require-extension simple-macros)

I tried the following example from SRFI-72:

aif.scm:

    (require-extension simple-macros)

    (define-syntax if-it
        (lambda (x)
          (syntax-case x ()
            ((k e1 e2 e3)
             (with-syntax ((it (datum->syntax-object (syntax k) 'it)))
               (syntax (let ((it e1))
                         (if it e2 e3))))))))

However, when I try it:

$ csi -b aif.scm
  _______   _     __
 / ___/ /  (_)___/ /_____ ___
/ /__/ _ \/ / __/  '_/ -_) _ \
\___/_//_/_/\__/_/\_\\__/_//_/

Version 2, Build 2 - linux-unix-gnu-x86 - [ dload ]
(c)2000-2005 Felix L. Winkelmann
; loading aif.scm ...
; loading /usr/lib/chicken/simple-macros.so ...
Error: illegal non-atomic object: ()


Any ideas?

Thank you,

Andrew