diff --git a/acid-state.cabal b/acid-state.cabal
--- a/acid-state.cabal
+++ b/acid-state.cabal
@@ -7,7 +7,7 @@
 -- The package version. See the Haskell package versioning policy
 -- (http://www.haskell.org/haskellwiki/Package_versioning_policy) for
 -- standards guiding when and how versions should be incremented.
-Version:             0.6.1
+Version:             0.6.2
 
 -- A short (one-line) description of the package.
 Synopsis:            Add ACID guarantees to any serializable Haskell data structure.
diff --git a/src/Data/Acid/Abstract.hs b/src/Data/Acid/Abstract.hs
--- a/src/Data/Acid/Abstract.hs
+++ b/src/Data/Acid/Abstract.hs
@@ -94,9 +94,10 @@
 
 downcast :: Typeable1 sub => AcidState st -> sub st
 downcast AcidState{acidSubState = AnyState sub}
-  = case gcast1 (Just sub) of
-      Just (Just typed_sub_struct) -> typed_sub_struct `asTypeOf` result
-      Nothing -> error $ "Data.Acid: Invalid subtype cast: " ++ show tag ++ " -> " ++ show (typeOf1 result)
-  where result = undefined
-        tag = show (typeOf1 sub)
-
+  = r 
+ where
+   r = case gcast1 (Just sub) of
+         Just (Just x) -> x
+         Nothing ->
+           error $
+            "Data.Acid: Invalid subtype cast: " ++ show (typeOf1 sub) ++ " -> " ++ show (typeOf1 r)