[plt-scheme] errotrace in 4.0?

Does errortrace work in 4.0? I can't seem to get it to work.

Nothing happens if I give '-l errortrace' on the command line, and I 
mean my program isn't even run.
$ mzscheme -l errortrace x.ss
$

If I add (require errortrace) to my program I don't see any profiling 
information
#lang scheme

(require errortrace)

(profiling-enabled #t)

(define (foo n)
  (if (= n 0)
    0
    (+ n (foo (sub1 n)))))

(foo 200)

(output-profile-results #t #t)

$ mzscheme x.ss             
20100
Sorting profile data...
Total samples: 0