[plt-scheme] Debugger stepping between files?

Hi all,

I've recently split the project that I've been working on in
DrScheme 360 into multiple source files.  Module forms, provide
and require, and that's all been good.  The down-side seems
to be that I can't single-step across files, in the debugger.
Pressing the "step" button to call a function defined in another
file causes it to run to completion, or rather (in my current
case) to run until the program crashes, in that other file.  Is
it possible to track execution between files, somehow?

Cheers,

-- 
Andrew