yesod - getting the request body for a POST "Content-type: application/json"

Using yesod 0.8.0, I'm trying to retrieve the body of a post message from this example request:

curl -v -H "Accept: application/json" -H "Content-Type: application/json" -X POST -d '{"name":"oscar"}'    http://localhost:3000/user/xyz

in my handler the only way I see it is to use

(pp, files) <- runRequestBody

But this fails because of the content type. Is there another function to do this?