diff --git a/Control/Applicative/Backwards.hs b/Control/Applicative/Backwards.hs
--- a/Control/Applicative/Backwards.hs
+++ b/Control/Applicative/Backwards.hs
@@ -41,7 +41,7 @@
 import Prelude hiding (foldr, foldr1, foldl, foldl1, null, length)
 import Control.Applicative
 import Data.Foldable
-#if !(MIN_VERSION_base(4,8,0))
+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__)
 import Data.Traversable (Traversable(traverse, sequenceA))
 #endif
 
diff --git a/Control/Applicative/Lift.hs b/Control/Applicative/Lift.hs
--- a/Control/Applicative/Lift.hs
+++ b/Control/Applicative/Lift.hs
@@ -39,7 +39,7 @@
 
 import Control.Applicative
 import Data.Functor.Constant
-#if !(MIN_VERSION_base(4,8,0))
+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__)
 import Data.Foldable (Foldable(foldMap))
 import Data.Monoid (Monoid(..))
 import Data.Traversable (Traversable(traverse))
diff --git a/Control/Monad/Signatures.hs b/Control/Monad/Signatures.hs
--- a/Control/Monad/Signatures.hs
+++ b/Control/Monad/Signatures.hs
@@ -27,23 +27,27 @@
 -- introduced in "Control.Monad.Trans.Cont".
 -- Any lifting function @liftCallCC@ should satisfy
 --
--- * @'Control.Monad.Trans.Class.lift' (f k) = f' ('Control.Monad.Trans.Class.lift' . k) => 'Control.Monad.Trans.Class.lift' (cf f) = liftCallCC cf f'@
+-- @'Control.Monad.Trans.Class.lift' (f k) = f' ('Control.Monad.Trans.Class.lift' . k) => 'Control.Monad.Trans.Class.lift' (cf f) = liftCallCC cf f'@
 --
+-- This implies that on entry to the continuation any outer monad
+-- transformer effect inside @callCC@ will have been rolled back.
 type CallCC m a b = ((a -> m b) -> m a) -> m a
 
 -- | Signature of the @catchE@ operation,
 -- introduced in "Control.Monad.Trans.Except".
 -- Any lifting function @liftCatch@ should satisfy
 --
--- * @'Control.Monad.Trans.Class.lift' (cf m f) = liftCatch ('Control.Monad.Trans.Class.lift' . cf) ('Control.Monad.Trans.Class.lift' f)@
+-- @'Control.Monad.Trans.Class.lift' (cf m h) = liftCatch cf ('Control.Monad.Trans.Class.lift' m) ('Control.Monad.Trans.Class.lift' . h)@
 --
+-- This implies that on entry to the handler function any outer monad
+-- transformer effect inside @catchE@ will have been rolled back.
 type Catch e m a = m a -> (e -> m a) -> m a
 
 -- | Signature of the @listen@ operation,
 -- introduced in "Control.Monad.Trans.Writer".
 -- Any lifting function @liftListen@ should satisfy
 --
--- * @'Control.Monad.Trans.Class.lift' . liftListen = liftListen . 'Control.Monad.Trans.Class.lift'@
+-- @'Control.Monad.Trans.Class.lift' . liftListen = liftListen . 'Control.Monad.Trans.Class.lift'@
 --
 type Listen w m a = m a -> m (a, w)
 
@@ -51,6 +55,6 @@
 -- introduced in "Control.Monad.Trans.Writer".
 -- Any lifting function @liftPass@ should satisfy
 --
--- * @'Control.Monad.Trans.Class.lift' . liftPass = liftPass . 'Control.Monad.Trans.Class.lift'@
+-- @'Control.Monad.Trans.Class.lift' . liftPass = liftPass . 'Control.Monad.Trans.Class.lift'@
 --
 type Pass w m a =  m (a, w -> w) -> m a
diff --git a/Control/Monad/Trans/Accum.hs b/Control/Monad/Trans/Accum.hs
--- a/Control/Monad/Trans/Accum.hs
+++ b/Control/Monad/Trans/Accum.hs
@@ -35,8 +35,7 @@
     evalAccum,
     mapAccum,
     -- * The AccumT monad transformer
-    AccumT(AccumT),
-    runAccumT,
+    AccumT(..),
     execAccumT,
     evalAccumT,
     mapAccumT,
@@ -78,7 +77,8 @@
 #endif
 
 -- ---------------------------------------------------------------------------
--- | An accumulation monad parameterized by the type @w@ of output to accumulate.
+-- | An accumulation monad (non-strict) parameterized by the type @w@
+-- of output to accumulate.
 --
 -- This monad is a more complex extension of both the reader and writer
 -- monads.  The 'return' function produces the output 'mempty', while @m
@@ -145,21 +145,21 @@
 -- In applications requiring only the ability to accumulate an output and
 -- to inspect the output so far, it would be considerably more efficient
 -- to use a state monad transformer.
-newtype AccumT w m a = AccumT (w -> m (a, w))
+--
+-- @AccumT w m@ is strict if and only if @m@ is.
+newtype AccumT w m a = AccumT {
+    -- | Unwrap an accumulation computation.  For example, in the call
+    --
+    -- @    (value, locals) <- runAccumT action globals@
+    --
+    -- the action is fed an initial environment @globals@, and @locals@ is
+    -- the sum of all arguments to calls of 'add' executed by the action.
+    runAccumT :: w -> m (a, w)
+    }
 #if __GLASGOW_HASKELL__ >= 704
     deriving (Generic)
 #endif
 
--- | Unwrap an accumulation computation.  For example, in the call
---
--- @    (value, locals) <- runAccumT action globals@
---
--- the action is fed an initial environment @globals@, and @locals@ is
--- the sum of all arguments to calls of 'add' executed by the action.
-runAccumT :: AccumT w m a -> w -> m (a, w)
-runAccumT (AccumT f) = f
-{-# INLINE runAccumT #-}
-
 -- | Extract the output from an accumulation computation.
 --
 -- * @'execAccumT' m w = 'liftM' 'snd' ('runAccumT' m w)@
@@ -279,6 +279,9 @@
 {-# INLINE liftCallCC' #-}
 
 -- | Lift a @catchE@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @catchE@ discards any output from the body on entering
+-- the handler.
 liftCatch :: Catch e m (a, w) -> Catch e (AccumT w m) a
 liftCatch catchE m h =
     AccumT $ \ w -> runAccumT m w `catchE` \ e -> runAccumT (h e) w
diff --git a/Control/Monad/Trans/Cont.hs b/Control/Monad/Trans/Cont.hs
--- a/Control/Monad/Trans/Cont.hs
+++ b/Control/Monad/Trans/Cont.hs
@@ -64,7 +64,7 @@
 #endif
 
 {- |
-Continuation monad.
+The continuation monad, which is non-strict.
 @Cont r a@ is a CPS ("continuation-passing style") computation that produces an
 intermediate result of type @a@ within a CPS computation whose final result type
 is @r@.
@@ -139,6 +139,8 @@
 --
 -- 'ContT' is not a functor on the category of monads, and many operations
 -- cannot be lifted through it.
+--
+-- @ContT r m@ is strict if and only if @m@ is.
 newtype ContT r m a = ContT { runContT :: (a -> m r) -> m r }
 #if __GLASGOW_HASKELL__ >= 704
     deriving (Generic)
diff --git a/Control/Monad/Trans/Except.hs b/Control/Monad/Trans/Except.hs
--- a/Control/Monad/Trans/Except.hs
+++ b/Control/Monad/Trans/Except.hs
@@ -16,7 +16,8 @@
 -- Stability   :  experimental
 -- Portability :  portable
 --
--- This monad transformer extends a monad with the ability to throw exceptions.
+-- This monad transformer extends a monad with the ability to throw
+-- and catch exceptions.
 --
 -- A sequence of actions terminates normally, producing a value,
 -- only if none of the actions in the sequence throws an exception.
@@ -35,8 +36,7 @@
     mapExcept,
     withExcept,
     -- * The ExceptT monad transformer
-    ExceptT(ExceptT),
-    runExceptT,
+    ExceptT(..),
     mapExceptT,
     withExceptT,
     -- * Exception operations
@@ -45,6 +45,7 @@
     handleE,
     tryE,
     finallyE,
+    onE,
     -- * Lifting other operations
     liftCallCC,
     liftListen,
@@ -69,7 +70,7 @@
 #if MIN_VERSION_base(4,4,0)
 import Control.Monad.Zip (MonadZip(mzipWith))
 #endif
-#if !(MIN_VERSION_base(4,8,0))
+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__)
 import Data.Foldable (Foldable(foldMap))
 import Data.Monoid (Monoid(mempty, mappend))
 import Data.Traversable (Traversable(traverse))
@@ -78,9 +79,11 @@
 import GHC.Generics
 #endif
 
--- | The parameterizable exception monad.
+-- | The parameterizable exception monad, which is strict.
 --
--- Computations are either exceptions or normal values.
+-- Computations are either exceptions (of any type) or normal values.
+-- These computations are plain values, and are unrelated to the
+-- "Control.Exception" mechanism, which is tied to the 'IO' monad.
 --
 -- The 'return' function returns a normal value, while @>>=@ exits on
 -- the first exception.  For a variant that continues after an error
@@ -116,16 +119,19 @@
 
 -- | A monad transformer that adds exceptions to other monads.
 --
--- @ExceptT@ constructs a monad parameterized over two things:
+-- @ExceptT@ constructs a strict monad parameterized over two things:
 --
--- * e - The exception type.
+-- * e - An arbitrary exception type.
 --
 -- * m - The inner monad.
 --
+-- The monadic computations are a plain values.  They are unrelated to
+-- the "Control.Exception" mechanism, which is tied to the 'IO' monad.
+--
 -- The 'return' function yields a computation that produces the given
 -- value, while @>>=@ sequences two subcomputations, exiting on the
 -- first exception.
-newtype ExceptT e m a = ExceptT (m (Either e a))
+newtype ExceptT e m a = ExceptT { runExceptT :: m (Either e a) }
 #if __GLASGOW_HASKELL__ >= 710
     deriving (Generic, Generic1)
 #elif __GLASGOW_HASKELL__ >= 704
@@ -164,11 +170,6 @@
 instance (Show e, Show1 m, Show a) => Show (ExceptT e m a) where
     showsPrec = showsPrec1
 
--- | The inverse of 'ExceptT'.
-runExceptT :: ExceptT e m a -> m (Either e a)
-runExceptT (ExceptT m) = m
-{-# INLINE runExceptT #-}
-
 -- | Map the unwrapped computation using the given function.
 --
 -- * @'runExceptT' ('mapExceptT' f m) = f ('runExceptT' m)@
@@ -328,6 +329,14 @@
     closer
     either throwE return res
 {-# INLINE finallyE #-}
+
+-- | If the first action succeeds, return its value, ignoring the
+-- second action.  If the first action throws an exception, run the
+-- second action and then throw an exception, either the one thrown by
+-- the second action, if any, or the one thrown by the first action.
+onE :: (Monad m) => ExceptT e m a -> ExceptT e m b -> ExceptT e m a
+onE action1 action2 = action1 `catchE` \ e -> action2 >> throwE e
+{-# INLINE onE #-}
 
 -- | Lift a @callCC@ operation to the new monad.
 liftCallCC :: CallCC m (Either e a) (Either e b) -> CallCC (ExceptT e m) a b
diff --git a/Control/Monad/Trans/Identity.hs b/Control/Monad/Trans/Identity.hs
--- a/Control/Monad/Trans/Identity.hs
+++ b/Control/Monad/Trans/Identity.hs
@@ -54,7 +54,7 @@
 import Control.Monad.Zip (MonadZip(mzipWith))
 #endif
 import Data.Foldable
-#if !(MIN_VERSION_base(4,8,0))
+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__)
 import Data.Traversable (Traversable(traverse))
 #endif
 import Prelude hiding (foldr, foldr1, foldl, foldl1, null, length)
diff --git a/Control/Monad/Trans/Maybe.hs b/Control/Monad/Trans/Maybe.hs
--- a/Control/Monad/Trans/Maybe.hs
+++ b/Control/Monad/Trans/Maybe.hs
@@ -61,7 +61,7 @@
 import Control.Monad.Zip (MonadZip(mzipWith))
 #endif
 import Data.Maybe (fromMaybe)
-#if !(MIN_VERSION_base(4,8,0))
+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__)
 import Data.Foldable (Foldable(foldMap))
 import Data.Traversable (Traversable(traverse))
 #endif
@@ -69,8 +69,8 @@
 import GHC.Generics
 #endif
 
--- | The parameterizable maybe monad, obtained by composing an arbitrary
--- monad with the 'Maybe' monad.
+-- | The parameterizable maybe monad, a strict monad obtained by composing
+-- an arbitrary monad with the 'Maybe' monad.
 --
 -- Computations are actions that may produce a value or exit.
 --
diff --git a/Control/Monad/Trans/RWS/CPS.hs b/Control/Monad/Trans/RWS/CPS.hs
--- a/Control/Monad/Trans/RWS/CPS.hs
+++ b/Control/Monad/Trans/RWS/CPS.hs
@@ -409,6 +409,9 @@
 {-# INLINE liftCallCC' #-}
 
 -- | Lift a @catchE@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @catchE@ discards any output or changes to the state from
+-- the body on entering the handler.
 liftCatch :: Catch e m (a,s,w) -> Catch e (RWST r w s m) a
 liftCatch catchE m h =
     RWST $ \ r s w -> unRWST m r s w `catchE` \ e -> unRWST (h e) r s w
diff --git a/Control/Monad/Trans/RWS/Lazy.hs b/Control/Monad/Trans/RWS/Lazy.hs
--- a/Control/Monad/Trans/RWS/Lazy.hs
+++ b/Control/Monad/Trans/RWS/Lazy.hs
@@ -393,6 +393,9 @@
 {-# INLINE liftCallCC' #-}
 
 -- | Lift a @catchE@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @catchE@ discards any output or changes to the state from
+-- the body on entering the handler.
 liftCatch :: Catch e m (a,s,w) -> Catch e (RWST r w s m) a
 liftCatch catchE m h =
     RWST $ \ r s -> runRWST m r s `catchE` \ e -> runRWST (h e) r s
diff --git a/Control/Monad/Trans/RWS/Strict.hs b/Control/Monad/Trans/RWS/Strict.hs
--- a/Control/Monad/Trans/RWS/Strict.hs
+++ b/Control/Monad/Trans/RWS/Strict.hs
@@ -397,6 +397,9 @@
 {-# INLINE liftCallCC' #-}
 
 -- | Lift a @catchE@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @catchE@ discards any output or changes to the state from
+-- the body on entering the handler.
 liftCatch :: Catch e m (a,s,w) -> Catch e (RWST r w s m) a
 liftCatch catchE m h =
     RWST $ \ r s -> runRWST m r s `catchE` \ e -> runRWST (h e) r s
diff --git a/Control/Monad/Trans/Reader.hs b/Control/Monad/Trans/Reader.hs
--- a/Control/Monad/Trans/Reader.hs
+++ b/Control/Monad/Trans/Reader.hs
@@ -71,7 +71,7 @@
 import GHC.Generics
 #endif
 
--- | The parameterizable reader monad.
+-- | The parameterizable reader monad, which is non-strict.
 --
 -- Computations are functions of a shared environment.
 --
@@ -122,6 +122,8 @@
 --
 -- <<images/bind-ReaderT.svg>>
 --
+--
+-- @ReaderT r m@ is strict if and only if @m@ is.
 newtype ReaderT r m a = ReaderT { runReaderT :: r -> m a }
 #if __GLASGOW_HASKELL__ >= 710
     deriving (Generic, Generic1)
diff --git a/Control/Monad/Trans/Select.hs b/Control/Monad/Trans/Select.hs
--- a/Control/Monad/Trans/Select.hs
+++ b/Control/Monad/Trans/Select.hs
@@ -37,8 +37,7 @@
     runSelect,
     mapSelect,
     -- * The SelectT monad transformer
-    SelectT(SelectT),
-    runSelectT,
+    SelectT(..),
     mapSelectT,
     -- * Monad transformation
     selectToContT,
@@ -58,7 +57,7 @@
 import GHC.Generics
 #endif
 
--- | Selection monad.
+-- | The selection monad, which is non-strict.
 type Select r = SelectT r Identity
 
 -- | Constructor for computations in the selection monad.
@@ -83,16 +82,15 @@
 --
 -- 'SelectT' is not a functor on the category of monads, and many operations
 -- cannot be lifted through it.
-newtype SelectT r m a = SelectT ((a -> m r) -> m a)
+--
+-- @SelectT r m@ is strict if and only if @m@ is.
+newtype SelectT r m a = SelectT {
+    -- | Runs a @SelectT@ computation with a function for evaluating
+    -- answers to select a particular answer.
+    runSelectT :: (a -> m r) -> m a }
 #if __GLASGOW_HASKELL__ >= 704
     deriving (Generic)
 #endif
-
--- | Runs a @SelectT@ computation with a function for evaluating answers
--- to select a particular answer.  (The inverse of 'select'.)
-runSelectT :: SelectT r m a -> (a -> m r) -> m a
-runSelectT (SelectT g) = g
-{-# INLINE runSelectT #-}
 
 -- | Apply a function to transform the result of a selection computation.
 -- This has a more restricted type than the @map@ operations for other
diff --git a/Control/Monad/Trans/State/Lazy.hs b/Control/Monad/Trans/State/Lazy.hs
--- a/Control/Monad/Trans/State/Lazy.hs
+++ b/Control/Monad/Trans/State/Lazy.hs
@@ -64,6 +64,9 @@
     liftCatch,
     liftListen,
     liftPass,
+    -- * Conversion to and from the strict version
+    strictToLazyStateT,
+    lazyToStrictStateT,
     -- * Examples
     -- ** State monads
     -- $examples
@@ -78,6 +81,7 @@
 import Control.Monad.IO.Class
 import Control.Monad.Signatures
 import Control.Monad.Trans.Class
+import qualified Control.Monad.Trans.State.Strict as Strict
 #if MIN_VERSION_base(4,12,0)
 import Data.Functor.Contravariant
 #endif
@@ -336,6 +340,9 @@
 {-# INLINE liftCallCC' #-}
 
 -- | Lift a @catchE@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies
+-- that the lifted @catchE@ rolls back to the original state on entering
+-- the handler.
 liftCatch :: Catch e m (a,s) -> Catch e (StateT s m) a
 liftCatch catchE m h =
     StateT $ \ s -> runStateT m s `catchE` \ e -> runStateT (h e) s
@@ -354,6 +361,16 @@
     ~((a, f), s') <- runStateT m s
     return ((a, s'), f)
 {-# INLINE liftPass #-}
+
+-- | Convert from the strict version to the lazy version
+strictToLazyStateT :: Strict.StateT s m a -> StateT s m a
+strictToLazyStateT (Strict.StateT f) = StateT f
+{-# INLINE strictToLazyStateT #-}
+
+-- | Convert from the lazy version to the strict version
+lazyToStrictStateT :: StateT s m a -> Strict.StateT s m a
+lazyToStrictStateT (StateT f) = Strict.StateT f
+{-# INLINE lazyToStrictStateT #-}
 
 {- $examples
 
diff --git a/Control/Monad/Trans/State/Strict.hs b/Control/Monad/Trans/State/Strict.hs
--- a/Control/Monad/Trans/State/Strict.hs
+++ b/Control/Monad/Trans/State/Strict.hs
@@ -337,6 +337,9 @@
 {-# INLINE liftCallCC' #-}
 
 -- | Lift a @catchE@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies
+-- that the lifted @catchE@ rolls back to the original state on entering
+-- the handler.
 liftCatch :: Catch e m (a,s) -> Catch e (StateT s m) a
 liftCatch catchE m h =
     StateT $ \ s -> runStateT m s `catchE` \ e -> runStateT (h e) s
diff --git a/Control/Monad/Trans/Writer/CPS.hs b/Control/Monad/Trans/Writer/CPS.hs
--- a/Control/Monad/Trans/Writer/CPS.hs
+++ b/Control/Monad/Trans/Writer/CPS.hs
@@ -283,14 +283,18 @@
 {-# INLINE censor #-}
 
 -- | Uniform lifting of a @callCC@ operation to the new monad.
--- This version rolls back to the original state on entering the
--- continuation.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @callCC@ discards any output from the body on entering
+-- the saved continuation.
 liftCallCC :: CallCC m (a, w) (b, w) -> CallCC (WriterT w m) a b
 liftCallCC callCC f = WriterT $ \ w ->
     callCC $ \ c -> unWriterT (f (\ a -> WriterT $ \ _ -> c (a, w))) w
 {-# INLINE liftCallCC #-}
 
 -- | Lift a @catchE@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @catchE@ discards any output from the body on entering
+-- the handler.
 liftCatch :: Catch e m (a, w) -> Catch e (WriterT w m) a
 liftCatch catchE m h = WriterT $ \ w ->
     unWriterT m w `catchE` \ e -> unWriterT (h e) w
diff --git a/Control/Monad/Trans/Writer/Lazy.hs b/Control/Monad/Trans/Writer/Lazy.hs
--- a/Control/Monad/Trans/Writer/Lazy.hs
+++ b/Control/Monad/Trans/Writer/Lazy.hs
@@ -70,7 +70,7 @@
 #endif
 import Data.Foldable
 import Data.Monoid
-#if !(MIN_VERSION_base(4,8,0))
+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__)
 import Data.Traversable (Traversable(traverse))
 #endif
 import Prelude hiding (null, length)
@@ -317,6 +317,9 @@
 {-# INLINE censor #-}
 
 -- | Lift a @callCC@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @callCC@ discards any output from the body on entering
+-- the saved condinuation.
 liftCallCC :: (Monoid w) => CallCC m (a,w) (b,w) -> CallCC (WriterT w m) a b
 liftCallCC callCC f = WriterT $
     callCC $ \ c ->
@@ -324,6 +327,9 @@
 {-# INLINE liftCallCC #-}
 
 -- | Lift a @catchE@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @catchE@ discards any output from the body on entering
+-- the handler.
 liftCatch :: Catch e m (a,w) -> Catch e (WriterT w m) a
 liftCatch catchE m h =
     WriterT $ runWriterT m `catchE` \ e -> runWriterT (h e)
diff --git a/Control/Monad/Trans/Writer/Strict.hs b/Control/Monad/Trans/Writer/Strict.hs
--- a/Control/Monad/Trans/Writer/Strict.hs
+++ b/Control/Monad/Trans/Writer/Strict.hs
@@ -73,7 +73,7 @@
 #endif
 import Data.Foldable
 import Data.Monoid
-#if !(MIN_VERSION_base(4,8,0))
+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__)
 import Data.Traversable (Traversable(traverse))
 #endif
 import Prelude hiding (null, length)
@@ -320,6 +320,9 @@
 {-# INLINE censor #-}
 
 -- | Lift a @callCC@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @callCC@ discards any output from the body on entering
+-- the saved continuation.
 liftCallCC :: (Monoid w) => CallCC m (a,w) (b,w) -> CallCC (WriterT w m) a b
 liftCallCC callCC f = WriterT $
     callCC $ \ c ->
@@ -327,6 +330,9 @@
 {-# INLINE liftCallCC #-}
 
 -- | Lift a @catchE@ operation to the new monad.
+-- The uniformity property (see "Control.Monad.Signatures") implies that
+-- the lifted @catchE@ discards any output from the body on entering
+-- the handler.
 liftCatch :: Catch e m (a,w) -> Catch e (WriterT w m) a
 liftCatch catchE m h =
     WriterT $ runWriterT m `catchE` \ e -> runWriterT (h e)
diff --git a/Data/Functor/Constant.hs b/Data/Functor/Constant.hs
--- a/Data/Functor/Constant.hs
+++ b/Data/Functor/Constant.hs
@@ -36,7 +36,7 @@
 
 import Control.Applicative
 import Data.Foldable
-#if !(MIN_VERSION_base(4,8,0))
+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__)
 import Data.Monoid (Monoid(..))
 import Data.Traversable (Traversable(traverse))
 #endif
diff --git a/Data/Functor/Reverse.hs b/Data/Functor/Reverse.hs
--- a/Data/Functor/Reverse.hs
+++ b/Data/Functor/Reverse.hs
@@ -43,7 +43,7 @@
 import qualified Control.Monad.Fail as Fail
 #endif
 import Data.Foldable
-#if !(MIN_VERSION_base(4,8,0))
+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__)
 import Data.Traversable (Traversable(traverse))
 #endif
 import Data.Monoid
diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,5 +1,18 @@
 -*-change-log-*-
 
+0.6.3.0 Ross Paterson <R.Paterson@city.ac.uk> Jan 2026
+	* Add Control.Monad.Trans.Except.onE
+	* Add strictToLazyState and lazyToStrictStateT
+
+0.6.2.0 Ross Paterson <R.Paterson@city.ac.uk> Apr 2025
+	* Redefine runAccumT, runExceptT and runSelectT as fields
+	* Document strictness of some transformers
+
+0.6.1.2 Ross Paterson <R.Paterson@city.ac.uk> Sep 2024
+	* Portability fixes for MicroHs
+	* Include image files in the bundle
+	* Expand ExceptT documentation
+
 0.6.1.1 Ross Paterson <R.Paterson@city.ac.uk> Aug 2023
 	* Additions to documentation, especially of AccumT.
 
diff --git a/transformers.cabal b/transformers.cabal
--- a/transformers.cabal
+++ b/transformers.cabal
@@ -1,5 +1,5 @@
 name:         transformers
-version:      0.6.1.1
+version:      0.6.3.0
 license:      BSD3
 license-file: LICENSE
 author:       Andy Gill, Ross Paterson
@@ -32,11 +32,10 @@
     introduced by monad transformers through other transformers.
 build-type: Simple
 extra-doc-files:
+    changelog
     images/bind-AccumT.svg
     images/bind-ReaderT.svg
     images/bind-WriterT.svg
-extra-source-files:
-    changelog
 cabal-version: 1.18
 
 source-repository head
@@ -47,13 +46,13 @@
   default-language: Haskell2010
   build-depends: base >= 2 && < 6
   hs-source-dirs: .
-  if !impl(ghc>=7.9)
+  if impl(ghc<7.9)
     -- Data.Functor.Identity was moved into base-4.8.0.0 (GHC 7.10)
     -- see also https://ghc.haskell.org/trac/ghc/ticket/9664
     -- NB: using impl(ghc>=7.9) instead of fragile Cabal flags
     hs-source-dirs: legacy/pre709
     exposed-modules: Data.Functor.Identity
-  if !impl(ghc>=7.11)
+  if impl(ghc<7.11)
     -- modules moved into base-4.9.0 (GHC 8.0)
     -- see https://ghc.haskell.org/trac/ghc/ticket/10773
     -- see https://ghc.haskell.org/trac/ghc/ticket/11135
@@ -66,7 +65,7 @@
       Data.Functor.Sum
   if impl(ghc>=7.2 && <7.5)
     -- Prior to GHC 7.5, GHC.Generics lived in ghc-prim
-    build-depends: ghc-prim
+    build-depends: ghc-prim < 0.3
   exposed-modules:
     Control.Applicative.Backwards
     Control.Applicative.Lift