carrierwave + grape uploading an image from hashie mash

Question

I have a hashie mash with filename, head, name, content-type, type, etc.

#<Hashie::Mash filename="modreal.jpg" head="Content-Disposition: form-data; name=\"image\"; filename=\"modreal.jpg\"\r\nContent-Type: image/jpeg\r\nContent-Length: 2406\r\n" name="image" tempfile=#<File:/var/folders/rh/rhhOCPJ9FOuqAbQjZPZh4k+++TI/-Tmp-/RackMultipart20131209-79188-1duiwwh> type="image/jpeg">

And I'm getting the following error when trying to give it to carrierwave.

 ArgumentError:
   expected instance of IO, StringIO, Tempfile or String, got Hashie::Mash

However when I just give the tempfile, it doesn't pass the extension whitelist. How can I make this work?