[plt-scheme] MrEd program in a separate namespace

I'm trying to run a MrEd program in it's own namespace, but I get this error:

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[ecavazos at odyssey foo]$ mred -z
MrEd version 204, Copyright (c) 1995-2003 PLT
> (define *ns* (make-namespace-with-mred))
> (eval '(read-eval-print-loop) *ns*)
> (load "foo.scm")
controller.scm:6:2: compile: bad syntax; function application is not allowed, because no #%app syntax transformer is bound in: (syntax-rules () ((make-slider-callback/weight variable) (lambda (slider control-event) (set! var...
> 

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Am I going about this the wrong way?

MrEd