NantContrib VSSGet doesn't like property macro expansion in "path"

Exactly what it says in the subject line!

<vssget
  username="nant" 
  password="nant" 
  localpath="${LocalPath}"
  recursive="true" 
  replace="true" 
  writable="true" 
  removedeleted="false" 
  dbpath="${DBPath}"
  path="${VSSPath}"
/>

For some reason, that I've yet to discover - and doesn't appear to be documented in the nantcontrib documentation, the "localpath" and "dbpath" properties will merrily accept nant property expansion, but the path won't. Grrr! Thusly I get an error as below when I run the script:

The "path" and/or "version" is not valid.