[plt-scheme] highlighting errors

Hi,
When a proc imported from a compiled module (zo-file) , calls error, the 
form that called the proc is highlighted. When the module is not compiled, 
the form is not highlighted. How can this be? Is this intensional? (I use 
version 209, Pretty-big)

((((lambda(x)((((((x x)x)x)x)x)x))
   (lambda(x)(lambda(y)(x(x y)))))
  (lambda(x)(write x)x))
 "greetings, Jos")