diff --git a/cereal.cabal b/cereal.cabal
--- a/cereal.cabal
+++ b/cereal.cabal
@@ -1,5 +1,5 @@
 name:                   cereal
-version:                0.4.0.1
+version:                0.4.1.0
 license:                BSD3
 license-file:           LICENSE
 author:                 Lennart Kolmodin <kolmodin@dtek.chalmers.se>,
@@ -20,10 +20,7 @@
                         tests/Tests.hs
 description:
   A binary serialization library, similar to binary, that introduces an isolate
-  primitive for parser isolation, and replaces the asynchronous errors with a
-  user-handleable Either type.  Similar to binary in performance, but uses a
-  strict ByteString instead of a lazy ByteString, thus restricting it to
-  operating on finite inputs.
+  primitive for parser isolation, and labeled blocks for better error messages.
 
 source-repository head
   type:     git
diff --git a/src/Data/Serialize.hs b/src/Data/Serialize.hs
--- a/src/Data/Serialize.hs
+++ b/src/Data/Serialize.hs
@@ -33,6 +33,7 @@
     , encode, encodeLazy
     , decode, decodeLazy
 
+    , expect
     , module Data.Serialize.Get
     , module Data.Serialize.Put
     , module Data.Serialize.IEEE754
@@ -111,6 +112,16 @@
 -- structure.
 decodeLazy :: Serialize a => L.ByteString -> Either String a
 decodeLazy  = runGetLazy get
+
+
+------------------------------------------------------------------------
+-- Combinators
+
+-- | Perform an action, failing if the read result does not match the argument
+--   provided.
+expect :: (Eq a, Serialize a) => a -> Get a
+expect x = get >>= \y -> if x == y then return x else mzero
+
 
 ------------------------------------------------------------------------
 -- Simple instances
diff --git a/src/Data/Serialize/Builder.hs b/src/Data/Serialize/Builder.hs
--- a/src/Data/Serialize/Builder.hs
+++ b/src/Data/Serialize/Builder.hs
@@ -67,7 +67,7 @@
 import qualified Data.ByteString.Internal as S
 
 #if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
-import GHC.Base
+import GHC.Base (Int(..), uncheckedShiftRL#)
 import GHC.Word (Word32(..),Word16(..),Word64(..))
 
 #if WORD_SIZE_IN_BITS < 64 && __GLASGOW_HASKELL__ >= 608
diff --git a/src/Data/Serialize/Get.hs b/src/Data/Serialize/Get.hs
--- a/src/Data/Serialize/Get.hs
+++ b/src/Data/Serialize/Get.hs
@@ -267,22 +267,18 @@
 -- Lazy Get --------------------------------------------------------------------
 
 runGetLazy' :: Get a -> L.ByteString -> (Either String a,L.ByteString)
-runGetLazy' m lstr = loop run (L.toChunks lstr)
+runGetLazy' m lstr = loop (Partial (runGetPartial m)) (L.toChunks lstr)
   where
-  remLen c = fromIntegral (L.length lstr) - B.length c
-  run str  = unGet m str Nothing (Incomplete (Just (remLen str))) failK finalK
 
-  loop k chunks = case chunks of
+  loop result chunks = case result of
 
-    c:cs -> case k c of
-      Fail str rest -> (Left str,L.fromChunks [rest])
-      Partial k'    -> loop k' cs
-      Done r c'     -> (Right r,L.fromChunks (c':cs))
+    Fail str rest -> (Left str, L.fromChunks (rest : chunks))
 
-    [] -> case k B.empty of
-      Fail str rest -> (Left str,L.fromChunks [rest])
-      Partial _     -> (Left "Failed reading: Internal error: unexpected end of input",L.empty)
-      Done r rest   -> (Right r,L.fromChunks [rest])
+    Partial k     -> case chunks of
+                       c:cs -> loop (k c)       cs
+                       []   -> loop (k B.empty) []
+
+    Done r rest   -> (Right r, L.fromChunks (rest : chunks))
 {-# INLINE runGetLazy' #-}
 
 -- | Run the Get monad over a Lazy ByteString.  Note that this will not run the