[Haskell-cafe] DeepSeq and random generators

I'm having trouble using Control.DeepSeq.force (necessary for parallel code) on a StdGen from System.Random. I don't know how to derive NFData. A standalone deriving statement, like this deriving instance NFData StdGen gets me the error "the data constructors of StdGen are not all in scope..." Is it actually possible to derive an NFData instance of StdGen, and how would I do that? Or if not possible, how can I work about this? Note: I'm going to see if I can use tf-random in this application. Maybe it will be easier. D