JSON Plugin - excludeProperties Issues

I am trying to specify properties for the JSON plugin to ignore.
However, this does not seem to be working.  Am I specfiying something
incorrectly?  Does it not work in conjunction with specifying the root?

                        <result type="json">
  <param
name="root">categoryChildren</param>
                                <param name="excludeProperties">
                                        createdTs, createdBy,
lastModifiedTs, lastModifiedBy, allCategoriesOfRoot,
                                        products, contracts, children,
contractCount, productCount,
                                        allTaxonomyCategories,
rootTaxonomyCategories
  </param>
                        </result>