Issues with Windows::Networking::BackgroundTransfer::CreateDownload

Question

There is a Uri to a file that may be local or online.
I'm attempting to download it.
If I use an online url, my code behaves as expected.
When I use the following style Uri, it fails
   "ms-appdata:///local/test.text"

I have verified that the file is in my AppDir\LocalState directory.

When I call

DownloadOperation^ downloadOp = downloader->CreateDownload( ref new Windows::Foundation::Uri( "ms-appdata:///local/test.text"/ ), file );

is throws the following exception:

Microsoft C++ exception: Platform::InvalidArgumentException ^ at memory location 0x03d3d6e4.
 The parameter is incorrect.

I cannot figure out what is wrong with that parameter.

Thanks
John.