diff --git a/RJson.cabal b/RJson.cabal
--- a/RJson.cabal
+++ b/RJson.cabal
@@ -1,5 +1,5 @@
 Name:          RJson
-Version:       0.2
+Version:       0.3
 Cabal-Version: >= 1.2
 License:       BSD3
 License-File:  LICENSE
diff --git a/Text/RJson.hs b/Text/RJson.hs
--- a/Text/RJson.hs
+++ b/Text/RJson.hs
@@ -1,4 +1,11 @@
-{-# OPTIONS_GHC -XFlexibleInstances -XOverlappingInstances -XMultiParamTypeClasses -XFlexibleContexts -XUndecidableInstances -XTemplateHaskell #-}
+{-# OPTIONS_GHC
+    -XFlexibleInstances
+    -XOverlappingInstances
+    -XMultiParamTypeClasses
+    -XFlexibleContexts
+    -XUndecidableInstances
+    -XTemplateHaskell
+    -cpp #-}
 
 module Text.RJson (TranslateField,
                    TranslateFieldD,
@@ -134,7 +141,7 @@
 stripInitialUnderscores ('_':s) = stripInitialUnderscores s
 stripInitialUnderscores s       = s
 
-instance (Data TranslateFieldD a) => TranslateField a where
+instance Typeable a => TranslateField a where
     translateField _ x = stripInitialUnderscores x
 
 
@@ -143,7 +150,7 @@
 --
 -- | New instances can be added to this class to customize
 --   JSON serialization.
-class ToJson a where
+class TranslateField a => ToJson a where
     toJson :: a -> JsonData
 
     -- For lists (same trick used by the Prelude to allow special
@@ -186,7 +193,7 @@
 -- Again, note inclusion of translateField from TranslateField,
 -- and TranslateField qualification on variable 't' (in addition
 -- to the expected ToJson qualification).
-instance (TranslateField t, ToJson t) => Sat (ToJsonD t) where
+instance ToJson t => Sat (ToJsonD t) where
     dict = ToJsonD { toJsonD          = toJson,
                      excludeD         = exclude,
                      arrayPrependD    = arrayPrepend,
@@ -209,26 +216,31 @@
 --    toJson i = JDNumber (floatToDouble i)
 instance ToJson Double where
     toJson i = JDNumber i
-instance Integral a => ToJson (Ratio a) where
+instance (Integral a, TranslateField a, Typeable a) => ToJson (Ratio a) where
     toJson i = JDNumber $ (fromIntegral (numerator i)) / (fromIntegral (denominator i))
                         
 instance ToJson Char where
     lToJson s = JDString s
     toJson c = JDString [c]
 
-instance ToJson a => ToJson (M.Map String a) where
+instance (ToJson a, TranslateField a, Data TranslateFieldD (M.Map String a))
+         => ToJson (M.Map String a) where
     toJson x = JDObject (M.map toJson x)
 
-instance (Typeable a, ToJson a) => ToJson [a] where
+instance (ToJson a, TranslateField a, Typeable a) => ToJson [a] where
     toJson = lToJson
 
 -- TODO: Add instances for the other array types supported by GHC.
-instance (Typeable a, ToJson a, Ix i) => ToJson (Array i a) where
+instance (ToJson a, TranslateField a, Typeable a, Typeable i, Ix i) => ToJson (Array i a) where
     toJson a = toJson (elems a)
 
 -- | Use this for merging two or more records together.
 --   Sensible instances of FromJson and ToJson are already defined for this type.
 data Union a b = Union a b deriving Show
+$(derive[''Union]) -- In order to derive (Typeable2 Union).
+                   -- It seems that we get away with overwriting the instance
+                   -- of Data that this creates (if we didn't, we could always
+                   -- instantiate Typeable manually for Union).
 -- | Nested Unions are left-branching by convention (since this is what you get
 --   by using the constructor as an infix operator).
 type Union3 a b c = (Union (Union a b) c)
@@ -245,7 +257,7 @@
 isJDObject _            = False
 jdObjectMap (JDObject m) = m
 
-instance (ToJson a, ToJson b) => ToJson (Union a b) where
+instance (ToJson a, ToJson b, TranslateField a, TranslateField b, Typeable a, Typeable b, Typeable2 Union) => ToJson (Union a b) where
     toJson (Union x y) =
         let jx = toJson x
             jy = toJson y
@@ -273,45 +285,39 @@
         | True =
             error ("Unable to serialize the primitive type '" ++ typename x ++ "'")
 
+enumToJson :: (Data ToJsonD a, ToJson a, TranslateField a) => a -> JsonData
+enumToJson x
+    | isAlgType (dataTypeOf toJsonProxy x) = JDString (show (toConstr toJsonProxy x))
+    | True = error "Passed non-algebraic type to enumToJson"
+
 instance (Data ToJsonD t, TranslateField t) => ToJson t where
     toJson = genericToJson
 
--- Instances for tuples up to n=10.
+-- Instances for tuples up to n=7 (this limit it is set by the non-existence of Typeable8).
 -- Tuples are converted to (hetrogenous) JSON lists.
-instance (ToJson a, ToJson b) => ToJson (a, b) where
+#define I(x) ToJson x, Typeable x
+instance (I(a), I(b)) => ToJson (a, b) where
     toJson (a,b) = JDArray [toJson a, toJson b]
-instance (ToJson a, ToJson b, ToJson c) => ToJson (a,b,c) where
+instance (I(a), I(b), I(c)) => ToJson (a,b,c) where
     toJson (a,b,c) = JDArray [toJson a, toJson b, toJson c]
-instance (ToJson a, ToJson b, ToJson c, ToJson d) => ToJson (a,b,c,d) where
+instance (I(a), I(b), I(c), I(d)) => ToJson (a,b,c,d) where
     toJson (a,b,c,d) = JDArray [toJson a, toJson b, toJson c, toJson d]
-instance (ToJson a, ToJson b, ToJson c, ToJson d, ToJson e) => ToJson (a,b,c,d,e) where
+instance (I(a), I(b), I(c), I(d), I(e)) => ToJson (a,b,c,d,e) where
     toJson (a,b,c,d,e) = JDArray [toJson a, toJson b, toJson c, toJson d, toJson e]
-instance (ToJson a, ToJson b, ToJson c, ToJson d, ToJson e, ToJson f) =>
+instance (I(a), I(b), I(c), I(d), I(e), I(f)) =>
          ToJson (a,b,c,d,e,f) where
     toJson (a,b,c,d,e,f) = JDArray [toJson a, toJson b, toJson c, toJson d, toJson e,
                                    toJson f]
-instance (ToJson a, ToJson b, ToJson c, ToJson d, ToJson e, ToJson f, ToJson g) =>
+instance (I(a), I(b), I(c), I(d), I(e), I(f), I(g)) =>
          ToJson (a,b,c,d,e,f,g) where
     toJson (a,b,c,d,e,f,g) = JDArray [toJson a, toJson b, toJson c, toJson d, toJson e,
                                      toJson f, toJson g]
-instance (ToJson a, ToJson b, ToJson c, ToJson d, ToJson e, ToJson f, ToJson g, ToJson h) =>
-         ToJson (a,b,c,d,e,f,g,h) where
-    toJson (a,b,c,d,e,f,g,h) = JDArray [toJson a, toJson b, toJson c, toJson d, toJson e,
-                                       toJson f, toJson g, toJson h]
-instance (ToJson a, ToJson b, ToJson c, ToJson d, ToJson e, ToJson f, ToJson g, ToJson h, ToJson i) =>
-         ToJson (a,b,c,d,e,f,g,h,i) where
-    toJson (a,b,c,d,e,f,g,h,i) = JDArray [toJson a, toJson b, toJson c, toJson d, toJson e,
-                                         toJson f, toJson g, toJson h, toJson i]
-instance (ToJson a, ToJson b, ToJson c, ToJson d, ToJson e, ToJson f, ToJson g, ToJson h, ToJson i, ToJson j) =>
-         ToJson (a,b,c,d,e,f,g,h,i,j) where
-    toJson (a,b,c,d,e,f,g,h,i,j) = JDArray [toJson a, toJson b, toJson c, toJson d, toJson e,
-                                           toJson f, toJson g, toJson h, toJson i, toJson j]
-
+#undef I
 
 --
 -- FromJson
 --
-class FromJson a where
+class TranslateField a => FromJson a where
     fromJson :: a -> JsonData -> Either String a
 
     -- For lists (same trick used by the Prelude to allow special
@@ -332,7 +338,7 @@
 fromJsonProxy :: Proxy FromJsonD
 fromJsonProxy = error "'fromJsonProxy' should never be evaluated!"
 
-instance (FromJson t, TranslateField t) => Sat (FromJsonD t) where
+instance FromJson t => Sat (FromJsonD t) where
     dict = FromJsonD { fromJsonD = fromJson,
                        objectDefaultsD = objectDefaults,
                        translateFieldD'' = translateField }
@@ -344,7 +350,7 @@
     lFromJson _ (JDString s) = Right s
     lFromJson _ _            = Left "Bad fromJson conversion: Non-string to 'String'"
 
-instance FromJson a => FromJson [a] where
+instance (FromJson a, TranslateField a, Typeable a) => FromJson [a] where
     fromJson _ x = lFromJson undefined x
 
 instance FromJson Int where
@@ -365,7 +371,7 @@
     fromJson _ (JDNumber d) = Right d
     fromJson _ _            = Left "Bad fromJson conversion: Non-numeric to 'Double'"
 
-instance Integral a => FromJson (Ratio a) where
+instance (Typeable a, Integral a) => FromJson (Ratio a) where
     fromJson _ (JDNumber i) = Right (fromRational (toRational i))
     fromJson _ _            = Left "Bad fromJson conversion: Non-numeric to instance of 'Ratio'"
 
@@ -379,7 +385,7 @@
 -- TODO: Use monads instead of 'ifs' if possible (funky type errors
 -- which I haven't figured out yet, something to do with monomorphism
 -- in let bindings vs. lambda abstraction?).
-instance (FromJson a, FromJson b) => FromJson (Union a b) where
+instance (FromJson a, FromJson b, Typeable a, Typeable b, TranslateField a, TranslateField b) => FromJson (Union a b) where
     fromJson _ o@(JDObject _) =
         let r1 = fromJson undefined o
             r2 = fromJson undefined o
@@ -392,20 +398,21 @@
 tuperror :: Int -> Either String a
 tuperror n = Left $ Printf.printf "Bad fromJson conversion: attempt to convert something that was not a list of length %i to a %i-tuple" n n
 
-instance (FromJson a, FromJson b) => FromJson (a,b) where
+#define I(x) FromJson x, Typeable x, TranslateField x
+instance (I(a), I(b)) => FromJson (a,b) where
     fromJson _ (JDArray [x1,x2]) = do
       r1 <- fromJson undefined x1
       r2 <- fromJson undefined x2
       return (r1,r2)
     fromJson _ _ = tuperror 2
-instance (FromJson a, FromJson b, FromJson c) => FromJson (a,b,c) where
+instance (I(a), I(b), I(c)) => FromJson (a,b,c) where
     fromJson _ (JDArray [x1,x2,x3]) = do
       r1 <- fromJson undefined x1
       r2 <- fromJson undefined x2
       r3 <- fromJson undefined x3
       return (r1,r2,r3)
     fromJson _ _ = tuperror 3
-instance (FromJson a, FromJson b, FromJson c, FromJson d) => FromJson(a,b,c,d) where
+instance (I(a), I(b), I(c), I(d)) => FromJson(a,b,c,d) where
     fromJson _ (JDArray [x1,x2,x3,x4]) = do
       r1 <- fromJson undefined x1
       r2 <- fromJson undefined x2
@@ -413,7 +420,7 @@
       r4 <- fromJson undefined x4
       return (r1,r2,r3,r4)
     fromJson _ _ = tuperror 4
-instance (FromJson a, FromJson b, FromJson c, FromJson d, FromJson e) => FromJson (a,b,c,d,e) where
+instance (I(a), I(b), I(c), I(d), I(e)) => FromJson (a,b,c,d,e) where
     fromJson _ (JDArray [x1,x2,x3,x4,x5]) = do
       r1 <- fromJson undefined x1
       r2 <- fromJson undefined x2
@@ -422,7 +429,7 @@
       r5 <- fromJson undefined x5
       return (r1,r2,r3,r4,r5)
     fromJson _ _ = tuperror 5
-instance (FromJson a, FromJson b, FromJson c, FromJson d, FromJson e, FromJson f) =>
+instance (I(a), I(b), I(c), I(d), I(e), I(f)) =>
          FromJson (a,b,c,d,e,f) where
     fromJson _ (JDArray [x1,x2,x3,x4,x5,x6]) = do
       r1 <- fromJson undefined x1
@@ -433,7 +440,7 @@
       r6 <- fromJson undefined x6
       return (r1,r2,r3,r4,r5,r6)
     fromJson _ _ = tuperror 6
-instance (FromJson a, FromJson b, FromJson c, FromJson d, FromJson e, FromJson f, FromJson g) =>
+instance (I(a), I(b), I(c), I(d), I(e), I(f), I(g)) =>
          FromJson (a,b,c,d,e,f,g) where
     fromJson _ (JDArray [x1,x2,x3,x4,x5,x6,x7]) = do
       r1 <- fromJson undefined x1
@@ -445,48 +452,7 @@
       r7 <- fromJson undefined x7
       return (r1,r2,r3,r4,r5,r6,r7)
     fromJson _ _ = tuperror 7
-instance (FromJson a, FromJson b, FromJson c, FromJson d, FromJson e, FromJson f, FromJson g, FromJson h) =>
-         FromJson (a,b,c,d,e,f,g,h) where
-    fromJson _ (JDArray [x1,x2,x3,x4,x5,x6,x7,x8]) = do
-      r1 <- fromJson undefined x1
-      r2 <- fromJson undefined x2
-      r3 <- fromJson undefined x3
-      r4 <- fromJson undefined x4
-      r5 <- fromJson undefined x5
-      r6 <- fromJson undefined x6
-      r7 <- fromJson undefined x7
-      r8 <- fromJson undefined x8
-      return (r1,r2,r3,r4,r5,r6,r7,r8)
-    fromJson _ _ = tuperror 8
-instance (FromJson a, FromJson b, FromJson c, FromJson d, FromJson e, FromJson f, FromJson g, FromJson h, FromJson i) =>
-         FromJson (a,b,c,d,e,f,g,h,i) where
-    fromJson _ (JDArray [x1,x2,x3,x4,x5,x6,x7,x8,x9]) = do
-      r1 <- fromJson undefined x1
-      r2 <- fromJson undefined x2
-      r3 <- fromJson undefined x3
-      r4 <- fromJson undefined x4
-      r5 <- fromJson undefined x5
-      r6 <- fromJson undefined x6
-      r7 <- fromJson undefined x7
-      r8 <- fromJson undefined x8
-      r9 <- fromJson undefined x9
-      return (r1,r2,r3,r4,r5,r6,r7,r8,r9)
-    fromJson _ _ = tuperror 9
-instance (FromJson a, FromJson b, FromJson c, FromJson d, FromJson e, FromJson f, FromJson g, FromJson h, FromJson i, FromJson j) =>
-         FromJson (a,b,c,d,e,f,g,h,i,j) where
-    fromJson _ (JDArray [x1,x2,x3,x4,x5,x6,x7,x8,x9,x10]) = do
-      r1 <- fromJson undefined x1
-      r2 <- fromJson undefined x2
-      r3 <- fromJson undefined x3
-      r4 <- fromJson undefined x4
-      r5 <- fromJson undefined x5
-      r6 <- fromJson undefined x6
-      r7 <- fromJson undefined x7
-      r8 <- fromJson undefined x8
-      r9 <- fromJson undefined x9
-      r10 <- fromJson undefined x10
-      return (r1,r2,r3,r4,r5,r6,r7,r8,r9,r10)
-    fromJson _ _ = tuperror 10
+#undef I
 
 elemsOfMap :: Ord k => M.Map k v -> [k] -> Maybe [v]
 elemsOfMap _ [] = Just []
@@ -498,14 +464,14 @@
 type ErrorWithState e s a = ErrorT e (State s) a
 
 -- TODO: Not a very descriptive name. Oh well...
-m1 :: (Data FromJsonD a) => a -> ErrorWithState String [JsonData] a
-m1 dummy = do
+m1 :: (Data FromJsonD a) => ErrorWithState String [JsonData] a
+m1 = do
   jvl <- lift get
   (case jvl of
      []       -> throwError "Bad fromJson conversion: Not enough elements in JSON array to satisfy constructor"
      (jv:jvs) -> do
        lift $ put jvs
-       (case fromJsonD dict dummy jv of
+       (case fromJsonD dict (undefined :: a) jv of
           Left e  -> throwError e
           Right x -> return x))
 
@@ -522,7 +488,7 @@
        (case M.lookup stripped m of
           Nothing ->
             case M.lookup stripped defaults of
-              Nothing -> throwError $  "Bad fromJson conversion: Required field not present in JSON object" ++ stripped
+              Nothing -> throwError $  "Bad fromJson conversion: Required field not present in JSON object: "
               Just v  ->
                 case fromJsonD dict dummy v of
                   Left e  -> throwError e
@@ -536,18 +502,28 @@
 genericFromJson dummy (JDArray l) =
     case datarep (dataTypeOf fromJsonProxy dummy) of
       AlgRep (c:_) ->
-          evalState (runErrorT (gmapM fromJsonProxy m1 (fromConstr fromJsonProxy c))) (tail l)
+          evalState (runErrorT (fromConstrM fromJsonProxy m1 c)) (tail l)
       AlgRep _     -> Left "Bad fromJson conversion: Type with no constructors!"
       _            -> Left "Bad fromJson conversion: Non-algebraic datatype given to 'genericFromJson'"
 genericFromJson dummy (JDObject m) =
     case datarep (dataTypeOf fromJsonProxy dummy) of
       AlgRep (c:_) ->
           case constrFields c of
-            [] -> Left "Bad fromJson conversion: Attempt to convert JDObect to a non-record algebraic type"
+            [] -> Left $ "Bad fromJson conversion: Attempt to convert JDObect to a non-record algebraic type"
+            -- Can't use fromConstrM because we need to get dummy values of the
+            -- appropriate type for each argument of the constructor. This is unfortunate,
+            -- since it means that we get runtime errors for records with strict fields.
             fs -> evalState (runErrorT (gmapM fromJsonProxy (m2 (objectDefaultsD dict dummy)) (fromConstr fromJsonProxy c))) (m, fs)
       AlgRep _     -> Left "Bad fromJson conversion: Type with no constructors!"
       _            -> Left "Bad fromJson conversion: Non-algebraic datatype given to 'genericFromJson'"
 genericFromJson _ _ = Left "Bad fromJson conversion: Expecting JSON object or array"
+
+enumFromJson :: (Data FromJsonD a, Data TranslateFieldD a) => a -> JsonData -> Either String a
+enumFromJson dummy (JDString s) =
+    case fromConstrM fromJsonProxy Nothing (mkConstr (dataTypeOf fromJsonProxy dummy) s [] Prefix ) of
+      Nothing -> Left "Error in enumFromJson"
+      Just x -> Right x
+enumFromJson _ _ = Left "Non-string given to enumFromJson"
           
 instance (Data FromJsonD t, Data TranslateFieldD t) => FromJson t where
     fromJson = genericFromJson
@@ -748,10 +724,13 @@
 toJsonString :: ToJson a => a -> String
 toJsonString = show . toJson
 
+{-
 data Test = Foo | Bar deriving Show
 $(derive[''Test])
 data Test2 = Test2 Int Int deriving Show
 $(derive[''Test2])
-
-trans :: (Data FromJsonD a) => a -> Int
-trans _ = 7
+data Test4 = Test4 { z :: String } deriving Show
+$(derive[''Test4])
+data Test3 = Test3 { x :: Int, y :: Test4} deriving Show
+$(derive[''Test3])
+-}