question on lenses/prisms

prisms.hs

{-# LANGUAGE TemplateHaskell #-}

import Control.Lens
import Test.Hspec
import Control.Monad

data Gene = X {_ident::Int, _xx::String} | Y {_ident::Int, _yy::Char}

makeLenses ''Gene
makePrisms ''Gene

gen1 = X 123 "xx"
gen2 = Y 456 'y'


main :: IO ()
main = hspec spec

spec :: Spec
spec = do
  describe "testtest" $ do
    it "is prismable 4" $ (gen1 ^. xx) `shouldBe` "xx"
    it "is prismable 5" $ (gen1 ^? xx) `shouldBe` (Just "xx")

    it "is prismable 6" $ (gen2 ^. xx) `shouldBe` mzero   -- how to make this *not* typecheck…
    it "is prismable 7" $ (gen2 ^? xx) `shouldBe` Nothing -- …but this be okay?