[Haskell-cafe] Fighting the monad stack, MonadIO

For a small webapi binding I try to implement a session like monad by building a stack including BrowserAction from Network.Browser module as following: newtype RBAction a = RBAction { exec :: ErrorT String (StateT RBState BrowserAction) a } deriving (Functor, Monad, MonadState RBState) I would like the RBAction to implement MonadIO as well, but fight with the liftIO function for hours now, without success. Any idea how the implementation of liftIO could look like? Thanks for help, Adam