[plt-scheme] require errors

hello,

I am trying to require a planet package in an application that embedds
mzscheme, but it doesn't seem to work. so, i was wondering if there is
something that needs to be set up for this to work, or if its a bug.

for example, the following require form works in DrScheme and mzscheme
but fails using an embedded mzscheme. ..

(require (planet zzkt/xmpp))

cdddr: expects argument of type <cdddrable value>; given ("zzkt" "xmpp.ss")

 === context ===
embedded-resolver

(current-module-name-resolver)
#<procedure:embedded-resolver>

any suggestions as to what is going wrong?

regards,
nik