[Haskell-cafe] Using CatchIO on StateT

Greetings, I found The MonadCatchIO-mtl package while looking for a way to catch exceptions in my custom StateT s (ReaderT r IO) monad. CatchIO worked flawlessly when handlers used the environment r from Reader, but things broken when I tried to use state. According to source, the handler is run with the same state which was passed to runStateT. instance MonadCatchIO m => MonadCatchIO (StateT s m) where m `catch` f = StateT $ \s -> (runStateT m s) `Control.Monad.CatchIO.catch` (\e -> runStateT (f e) s) And my finalizing action depends on the current state. Can you give an advice how to get the behavior I need? Best regards, Dmitry Vyal