ASDF; systems without files but with performs don't perform...

Systems without files never do their perform steps... For example, if  
I have a system like:

> (in-package asdf)
>
> (defsystem foo
>   :perform (load-op :after (op c)
>                     (print "hi")))
>

and then do (asdf:oos asdf:load-op 'foo), "hi" won't be printed  
because the perform won't be called because from ASDF's perspective,  
there is nothing to do. I.e., (traverse <load-op> <foo-system>)  
returns nil.

I'd call this a bug but perhaps it's by design... thoughts?
-- 
Gary Warren King
metabang.com
http://www.metabang.com/