[Haskell-cafe] Strict evaluation not working?

Hi, having found a bit of time to play with Haskell, I am trying to figure out how to enforce strict evaluation. I wrote the following program: main = let x = zipWith (+) [5..] [6..] in putStrLn $ show $ x `seq` head x I expected this program not to terminate - because of the seq-Operator, but it happily returns 11 in ghc as well as in ghci. What do I make wrong? Chris