diff --git a/Control/Concurrent/STM/TArray.hs b/Control/Concurrent/STM/TArray.hs
--- a/Control/Concurrent/STM/TArray.hs
+++ b/Control/Concurrent/STM/TArray.hs
@@ -1,4 +1,6 @@
 {-# OPTIONS -fglasgow-exts #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Concurrent.STM.TArray
@@ -22,6 +24,7 @@
 import Data.Array.Base (listArray, arrEleBottom, unsafeAt, MArray(..),
                         IArray(numElements))
 import Data.Ix (rangeSize)
+import Data.Typeable (Typeable)
 import Control.Concurrent.STM.TVar (TVar, newTVar, readTVar, writeTVar)
 #ifdef __GLASGOW_HASKELL__
 import GHC.Conc (STM)
@@ -36,7 +39,7 @@
 -- but it may be replaced by a more efficient implementation in the future
 -- (the interface will remain the same, however).
 --
-newtype TArray i e = TArray (Array i (TVar e))
+newtype TArray i e = TArray (Array i (TVar e)) deriving (Eq, Typeable)
 
 instance MArray TArray e STM where
     getBounds (TArray a) = return (bounds a)
diff --git a/Control/Concurrent/STM/TChan.hs b/Control/Concurrent/STM/TChan.hs
--- a/Control/Concurrent/STM/TChan.hs
+++ b/Control/Concurrent/STM/TChan.hs
@@ -1,4 +1,6 @@
 {-# OPTIONS_GHC -fno-warn-name-shadowing #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Concurrent.STM.TChan
@@ -31,8 +33,10 @@
 #ifdef __GLASGOW_HASKELL__
 import GHC.Conc
 
+import Data.Typeable (Typeable)
+
 -- | 'TChan' is an abstract type representing an unbounded FIFO channel.
-data TChan a = TChan (TVar (TVarList a)) (TVar (TVarList a))
+data TChan a = TChan (TVar (TVarList a)) (TVar (TVarList a)) deriving Typeable
 
 type TVarList a = TVar (TList a)
 data TList a = TNil | TCons a (TVarList a)
diff --git a/Control/Concurrent/STM/TMVar.hs b/Control/Concurrent/STM/TMVar.hs
--- a/Control/Concurrent/STM/TMVar.hs
+++ b/Control/Concurrent/STM/TMVar.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Concurrent.STM.TMVar
@@ -34,7 +36,9 @@
 #ifdef __GLASGOW_HASKELL__
 import GHC.Conc
 
-newtype TMVar a = TMVar (TVar (Maybe a))
+import Data.Typeable (Typeable)
+
+newtype TMVar a = TMVar (TVar (Maybe a)) deriving (Eq, Typeable)
 {- ^
 A 'TMVar' is a synchronising variable, used
 for communication between concurrent threads.  It can be thought of
diff --git a/Control/Concurrent/STM/TVar.hs b/Control/Concurrent/STM/TVar.hs
--- a/Control/Concurrent/STM/TVar.hs
+++ b/Control/Concurrent/STM/TVar.hs
@@ -30,3 +30,7 @@
 #else
 import Control.Sequential.STM
 #endif
+
+#if ! MIN_VERSION_base(4,2,0)
+readTVarIO = atomically . readTVar
+#endif
diff --git a/Control/Monad/STM.hs b/Control/Monad/STM.hs
--- a/Control/Monad/STM.hs
+++ b/Control/Monad/STM.hs
@@ -36,15 +36,19 @@
 
 #ifdef __GLASGOW_HASKELL__
 import GHC.Conc
+#if ! MIN_VERSION_base(4,3,0)
 import Control.Monad	( MonadPlus(..) )
+#endif
 #else
 import Control.Sequential.STM
 #endif
 
 #ifdef __GLASGOW_HASKELL__
+#if ! MIN_VERSION_base(4,3,0)
 instance MonadPlus STM where
   mzero = retry
   mplus = orElse
+#endif
 
 check :: Bool -> STM a
 check b = if b then return undefined else retry
diff --git a/Control/Sequential/STM.hs b/Control/Sequential/STM.hs
--- a/Control/Sequential/STM.hs
+++ b/Control/Sequential/STM.hs
@@ -9,6 +9,7 @@
     ) where
 
 import Prelude hiding (catch)
+import Control.Applicative (Applicative(pure, (<*>)))
 import Control.Exception
 import Data.IORef
 
@@ -21,8 +22,12 @@
 instance Functor STM where
     fmap f (STM m) = STM (fmap f . m)
 
+instance Applicative STM where
+    pure = STM . const . pure
+    STM mf <*> STM mx = STM $ \ r -> mf r <*> mx r
+
 instance Monad STM where
-    return x = STM (const (return x))
+    return = pure
     STM m >>= k = STM $ \ r -> do
 	x <- m r
 	unSTM (k x) r
diff --git a/stm.cabal b/stm.cabal
--- a/stm.cabal
+++ b/stm.cabal
@@ -1,5 +1,5 @@
 name:		stm
-version:	2.1.2.0
+version:	2.1.2.1
 license:	BSD3
 license-file:	LICENSE
 maintainer:	libraries@haskell.org