Hi Jarno A cursory look at the CouchMonad says it is build upon the IO monad so you won't be able to safely extract values out of it. This suggests that you should "run" HXT functions within the CouchMonad monad. The HXT library has various run_ functions - runIOLA, runSt, ... - to run a computation and produce a value. I don't know the HXT library, so don't know which particular run function to use, but a viable construction might look like one of these two: processReplacement elementId docId state0 = do node <- toXNode docId let ans = runSt (setNode node `when` idMatches elementId) state0 return ans Or maybe runIOLA: processReplacement elementId docId = do node <- toXNode docId ans <- runIOLA (setNode node `when` idMatches elementId) return ans Best wishes Stephen