diff --git a/README b/README
--- a/README
+++ b/README
@@ -1,6 +1,5 @@
 This is version 3 of 'monadLib'.
 The library is in the directory 'src'.
-In this directory we have bureaucratic overhead.
 
 Files
 ~~~~~
@@ -10,8 +9,9 @@
 Setup.hs            Used by the Cabal framework.
 monadLib.cabal      Used by the Cabal framework.
 
-src/MonadLib.hs     The library.
-src/Monads.hs       Definitions for some more base monads (optional).
+src/MonadLib.hs        The library.
+src/MonadLib/Derive.hs Definitions useful for monads defined with newtype.
+src/MonadLib/Monads.hs Definitions for some more base monads (optional).
 
 
 Simple Installation
diff --git a/monadLib.cabal b/monadLib.cabal
--- a/monadLib.cabal
+++ b/monadLib.cabal
@@ -1,5 +1,5 @@
 Name:           monadLib
-Version:        3.4.4
+Version:        3.4.5
 License:        BSD3
 License-file:   LICENSE
 Author:         Iavor S. Diatchki
@@ -13,7 +13,10 @@
 Build-type:     Simple
 Extra-source-files: LICENSE, README, CHANGES
 Exposed-modules: MonadLib, MonadLib.Monads, MonadLib.Derive
+
+
 Extensions:
-  MultiParamTypeClasses, FunctionalDependencies, Rank2Types
-GHC-options:    -O2 -W -fallow-undecidable-instances
+  MultiParamTypeClasses, FunctionalDependencies, Rank2Types,
+  UndecidableInstances
+GHC-options:    -O2 -W
 
diff --git a/src/MonadLib.hs b/src/MonadLib.hs
--- a/src/MonadLib.hs
+++ b/src/MonadLib.hs
@@ -8,7 +8,7 @@
   Id, Lift, IdT, ReaderT, WriterT,
   StateT,
   ExceptionT,
-  -- 
+  --
   -- $WriterM_ExceptionT
   ChoiceT, ContT,
 
@@ -43,6 +43,7 @@
 import Control.Applicative
 import Control.Monad
 import Control.Monad.Fix
+import Control.Monad.ST (ST)
 import qualified Control.Exception as IO (throwIO,try,Exception)
 import Data.Monoid
 import Prelude hiding (Ordering(..))
@@ -242,11 +243,12 @@
   -- | Promote a computation from the base monad.
   inBase :: n a -> m a
 
-instance BaseM IO IO        where inBase = id
-instance BaseM Maybe Maybe  where inBase = id
-instance BaseM [] []        where inBase = id
-instance BaseM Id Id        where inBase = id
-instance BaseM Lift Lift    where inBase = id
+instance BaseM IO IO         where inBase = id
+instance BaseM Maybe Maybe   where inBase = id
+instance BaseM [] []         where inBase = id
+instance BaseM Id Id         where inBase = id
+instance BaseM Lift Lift     where inBase = id
+instance BaseM (ST s) (ST s) where inBase = id
 
 
 instance (BaseM m n) => BaseM (IdT          m) n where inBase = t_inBase