Dear Cafe, I recently ran into a Haskell2010 parsing error with code that parses just fine under Haskell98, and it seems to me that this might be an unintended consequence. Briefly, I have runModel :: StdGen -> Model () -> Result where Model is a monadic type, and then my main was main :: IO () main = do gen <- getStdGen let log = runModel gen $ do initialize 72 report replicateM_ 50 $ do replicateM_251 migrate report putStr . format $ log Haskell 2010 doesn't like the additional level of indentation after the "let log" line. If I pull the content of the "do" into a separate definition, so this becomes let log = runModel gen simulate the parsing error goes away. Questions: 1) Is this intended? 2) Can this code be formatted in a way to make Haskell 2010 happy? Many thanks. Peace, Stu