[Haskell-cafe] Why the exception?

Cafe I'm a bit lost on this exception and curious about what's going on. Is there a valid reason for this exception that I am missing? Note the hard-coded [0..100] could be any Word8 list you want (generated via arbitrary, [], or other) and it gives the same result. Load the module and perform: :break prop_LPS quickCheck prop_LPS :step :force ps *** Exception: Prelude.head: empty list

import qualified Data.ByteString as L import Test.QuickCheck

instance Arbitrary L.ByteString where arbitrary = do return $ L.pack [0..100]

prop_LPS :: L.ByteString -> Bool prop_LPS ps = ps `seq` True

P.S. Same result with GHCi 6.8.2 and 6.8.3.