Punchout - Is there a way to default the category, when no category specified within the payload

Is there a way to default the category when returning a requisition from within Punchout, when the payload does not include any category itself? The "Default Category Name" is used when a mapping map set is in place and where the category value is passed within the payload but does not exist in the mapping. If a map set exists, and the default is specified, but no category is in the payload, the default is not used. Which looks to be intended functionality. Is there a way to workaround this and force the Default Category Name value to be applied?