diff --git a/HISTORY b/HISTORY
--- a/HISTORY
+++ b/HISTORY
@@ -1,3 +1,7 @@
+0.3     (2012-07-24)
+   change NonTermination to a custom BlockedIndefinitelyOnIVar exception,
+   and require base >= 4. (using NonTermination leads to <<loop>> messages)
+
 0.2     (2012-07-23)
    change BlockedIndefinitely exception (gone since ghc 7.0) to NonTermination
 
diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2008, 2009 Bertram Felgenhauer
+Copyright (c) 2008-2012 Bertram Felgenhauer
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/ivar-simple.cabal b/ivar-simple.cabal
--- a/ivar-simple.cabal
+++ b/ivar-simple.cabal
@@ -1,5 +1,5 @@
 Name:          ivar-simple
-Version:       0.2
+Version:       0.3
 Category:      Concurrency
 Stability:     experimental
 Copyright:     (c) 2008-2012 Bertram Felgenhauer
@@ -19,12 +19,13 @@
     HISTORY
 
 Library
-    HS-Source-Dirs:     src
+    Hs-Source-Dirs:
+        src
     Exposed-Modules:
         Data.IVar.Simple
         Data.IVar.Simple.IChan
         Data.IVar.Simple.MIChan
-    Build-Depends:      base < 5
-    -- workaround for http://hackage.haskell.org/trac/ghc/ticket/2756
-    if impl(ghc <= 6.10.1)
-        GHC-Options:        -fno-state-hack
+    Build-Depends:
+        base >= 4 && < 5
+    Extensions:
+        DeriveDataTypeable
diff --git a/src/Data/IVar/Simple.hs b/src/Data/IVar/Simple.hs
--- a/src/Data/IVar/Simple.hs
+++ b/src/Data/IVar/Simple.hs
@@ -1,6 +1,7 @@
+{-# LANGUAGE DeriveDataTypeable #-}
 -- |
 -- Module      : Data.IVar.Simple
--- Copyright   : (c) 2008-2012 Bertram Felgenhauer
+-- Copyright   : (c) 2008, 2009 Bertram Felgenhauer
 -- License     : BSD3
 --
 -- Maintainer  : Bertram Felgenhauer <int-e@gmx.de>
@@ -23,18 +24,20 @@
     tryRead,
     write,
     tryWrite,
+    BlockedIndefinitelyOnIVar,
 ) where
 
 import Control.Concurrent.MVar
 import Control.Exception
 import Control.Monad
+import Data.Typeable
 import System.IO.Unsafe
 import Prelude hiding (read)
 
 -- | A write-once (/immutable/) Variable
 data IVar a = IVar (MVar ()) (MVar a) a
 
--- | Creates a new, empty 'IVar'.
+-- | Create a new, empty 'IVar'.
 new :: IO (IVar a)
 new = do
     lock <- newMVar ()
@@ -53,30 +56,42 @@
 
 -- | Returns the value of an 'IVar'.
 --
--- The evaluation will block until a value is written to the 'IVar' if there
--- is no value yet.
+-- The evaluation will block until a value is written to the 'IVar' if it
+-- has no value yet.
 read :: IVar a -> a
 read (IVar _ _ value) = value
 
--- | Try to read an 'IVar'. Returns 'Nothing' if there is not value yet.
+-- | Try to read an 'IVar'. Returns 'Nothing' if it has no value yet.
 tryRead :: IVar a -> IO (Maybe a)
 tryRead (IVar lock _ value) = do
     empty <- isEmptyMVar lock
     if empty then return (Just value) else return Nothing
 
--- | Writes a value to an 'IVar'. Raises a 'NonTermination' exception if
--- it fails.
+-- | Writes a value to an 'IVar'. Raises a 'BlockedIndefinitelyOnIVar'
+-- exception if the variable already has a value.
 write :: IVar a -> a -> IO ()
 write ivar value = do
     result <- tryWrite ivar value
-    when (not result) $ throwIO NonTermination
+    when (not result) $ throwIO BlockedIndefinitelyOnIVar
 -- Note: It would be easier to block forever when the IVar is full. However,
 -- the thread would likely not be garbage collected then.
 
--- | Writes a value to an 'IVar'. Returns 'True' if successful.
+-- | Writes a value to an 'IVar'. Returns 'True' if successful, and
+-- 'False' otherwise.
 tryWrite :: IVar a -> a -> IO Bool
 tryWrite (IVar lock trans _) value = block $ do
     a <- tryTakeMVar lock
     case a of
         Just _  -> putMVar trans value >> return True
         Nothing -> return False
+
+-- | The thread has attempted to write to a full 'IVar'.
+data BlockedIndefinitelyOnIVar = BlockedIndefinitelyOnIVar
+    deriving (Typeable)
+
+instance Exception BlockedIndefinitelyOnIVar
+
+instance Show BlockedIndefinitelyOnIVar where
+    showsPrec _ BlockedIndefinitelyOnIVar =
+        showString "thread blocked indefinitely writing full IVar"
+
diff --git a/src/Data/IVar/Simple/IChan.hs b/src/Data/IVar/Simple/IChan.hs
--- a/src/Data/IVar/Simple/IChan.hs
+++ b/src/Data/IVar/Simple/IChan.hs
@@ -8,8 +8,8 @@
 -- Portability : ghc
 --
 -- An 'IChan's is a type of multicast channel built on top of 'IVar.IVar's.
--- It supports multiple readers. The 'IChan' data type represents the head
--- of a channel.
+-- It supports multiple readers. The channel is represented as a linked
+-- list. The 'IChan' data type represents the head of a channel.
 --
 -- Writing to an 'IChan' head has write-once semantics similar to 'IVar.IVar's:
 -- only the first of several attempts to write to the head will succeed,
@@ -45,8 +45,8 @@
 
 -- | Write a single value to the channel.
 --
--- Raises a 'NonTermination' exception if a value has already been
--- written to the channel. Otherwise, returns a new channel head for
+-- Raises a 'BlockedIndefinitelyOnIVar' exception if a value has already
+-- been written to the channel. Otherwise, returns a new channel head for
 -- writing further values.
 write :: IChan a -> a -> IO (IChan a)
 write (IChan as) a = do
diff --git a/src/Data/IVar/Simple/MIChan.hs b/src/Data/IVar/Simple/MIChan.hs
--- a/src/Data/IVar/Simple/MIChan.hs
+++ b/src/Data/IVar/Simple/MIChan.hs
@@ -1,6 +1,6 @@
 -- |
 -- Module      : Data.IVar.Simple.MIChan
--- Copyright   : (c) 2008, 2009 Bertram Felgenhauer
+-- Copyright   : (c) 2008-2012 Bertram Felgenhauer
 -- License     : BSD3
 --
 -- Maintainer  : Bertram Felgenhauer <int-e@gmx.de>
@@ -9,9 +9,9 @@
 --
 -- An 'MIChan' is a multicast channel built on top of an 'IChan.IChan'.
 --
--- Like 'IChan.IChan', this supports multiple readers. It is comparable to
--- a @Control.Concurrent.Chan.Chan@ for the writing end: Each write will
--- append an element to the channel. No writes will fail.
+-- Like 'IChan.IChan', this channel supports multiple readers. It is
+-- comparable to a @Control.Concurrent.Chan.Chan@ for the writing end:
+-- Each write will append an element to the channel. No writes will fail.
 
 module Data.IVar.Simple.MIChan (
     -- $comparison