[plt-scheme] Using extensions

I'm working on a set of database bindings for mzscheme and I've run into
some behavior I don't understand when mzscheme tries to load an
extension. Development is on a x86 Linux system (FC6, if it matters)
using mzscheme 352.

My current priority is a extension which uses SWIG-generated wrapper
code to wrap the Postgres client lib. The steps I've been using to
deploy and load the extension look like this:

1) Build the extension into a shared lib named pltpgdb.so. The name of
the module it provides is "pltpgdb".

2) Copy the resulting lib into compiled/native/i386-linux.

3) Fire up mzscheme and try to require the extension like so:

(require "pltpgdb")

mzscheme reports this error when the require statement is evaluated:

load-extension: expected module 'pltpgdb, but found module 'pltpgdb'

The error message confuses me since it seems to be finding the module
it's expecting.

Any suggestions?

Thanks,
Kevin