[Haskell-cafe] doctest: Interpreter exited with an error: ExitFailure 127

Hi, i have upgraded to doctest version 0.4.1. Now when i try to run the example from the webpage, i get: doctest: Interpreter exited with an error: ExitFailure 127 What's wrong here and how can i fix it? Kind regards Chris This is the content of Fib.hs: module Fib where -- | Compute Fibonacci numbers -- -- Examples: -- -- >>> fib 10 -- 55 -- -- >>> fib 5 -- 5 fib 0 = 0 fib 1 = 1 fib n = fib (n - 1) + fib (n - 2) main = do print $ fib 4