Using external jars in GWT projects (server-side)

Using external jars in GWT projects (server-side)

I am trying to use an external jar in a Google Web Toolkit project.
The jar is for use only on the server side. For reference it is the
jbcrypt jar packaged as org.mindrot.jbcrypt.
I have included the jar in my project's build path, and eclipse finds it
and resolves the BCrypt class in my project.
When I try to use the service that relies on this jar (a login service
that extends RemoteServiceServlet), I get a
com.google.gwt.user.server.rpc.UnexpectedException which is caused by a
NoClassDefFoundError for org.mindrot.jbcrypt.BCrypt.
Does the development server need the jar to be somewhere else? What should
I do? Thanks.