diff --git a/Data/Aeson/AutoType/CodeGen.hs b/Data/Aeson/AutoType/CodeGen.hs
--- a/Data/Aeson/AutoType/CodeGen.hs
+++ b/Data/Aeson/AutoType/CodeGen.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP               #-}
 {-# LANGUAGE OverloadedStrings #-}
 -- | Wrappers for generating prologue and epilogue code in Haskell.
 module Data.Aeson.AutoType.CodeGen(
@@ -45,7 +46,11 @@
   ,"import           Control.Applicative"
   ,"import           Data.Aeson.AutoType.Alternative"
   ,"import           Data.Aeson(decode, Value(..), FromJSON(..), ToJSON(..),"
+#if MIN_VERSION_aeson(0,11,0)
+  ,"                            pairs,"
+#endif
   ,"                            (.:), (.:?), (.=), object)"
+  ,"import           Data.Monoid"
   ,"import           Data.Text (Text)"
   ,"import           GHC.Generics" 
   ,""
diff --git a/Data/Aeson/AutoType/Format.hs b/Data/Aeson/AutoType/Format.hs
--- a/Data/Aeson/AutoType/Format.hs
+++ b/Data/Aeson/AutoType/Format.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                 #-}
 {-# LANGUAGE TemplateHaskell     #-}
 {-# LANGuaGE ScopedTypeVariables #-}
 {-# LANGUAGE ViewPatterns        #-}
@@ -18,6 +19,7 @@
 import           Control.Monad             (forM)
 import           Control.Exception(assert)
 import qualified Data.HashMap.Strict        as Map
+import           Data.Monoid
 import qualified Data.Set                   as Set
 import qualified Data.Text                  as Text
 import           Data.Text                 (Text)
@@ -98,14 +100,20 @@
 makeToJSON :: Text -> [MappedKey] -> Text
 makeToJSON identifier contents =
     Text.unlines [
-        Text.concat ["instance ToJSON ", identifier, " where"],
-        Text.concat ["  toJSON (", identifier, " {", wildcard, "}) = object [", inner, "]"]
+        Text.concat ["instance ToJSON ", identifier, " where"]
+      , Text.concat ["  toJSON     (", identifier, " {", wildcard, "}) = object [", inner ", ", "]"]
+#if MIN_VERSION_aeson(0,11,0)
+      , maybeToEncoding
+#endif
       ]
   where
+    maybeToEncoding | null contents = ""
+                    | otherwise     =
+                        Text.concat ["  toEncoding (", identifier, " {", wildcard, "}) = pairs  (", inner "<>", ")"]
     wildcard | null contents = ""
              | otherwise     = ".."
-    inner = ", " `Text.intercalate`
-              map putValue contents
+    inner separator = separator `Text.intercalate`
+                      map putValue contents
     putValue (jsonId, haskellId, _typeText, _nullable) = Text.unwords [escapeText jsonId, ".=", haskellId]
     escapeText = Text.pack . show . Text.unpack
 -- Contents example for wrapToJSON
@@ -165,7 +173,7 @@
 -- the separate declarations on which this one is dependent.
 formatType :: Type -> DeclM Text
 formatType  TString                          = return "Text"
-formatType  TNum                             = return "Int"
+formatType  TNum                             = return "Double"
 formatType  TBool                            = return "Bool"
 formatType (TLabel l)                        = return $ normalizeTypeName l
 formatType (TUnion u)                        = wrap <$> case length nonNull of
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,9 +1,13 @@
 Changelog
 =========
+    1.0.12  Mar 2016
+
+        * Fixed issue #8 - misrepresenting Double as Int.
+        * Fixed issue #9 - efficient formatting with new Aeson-0.10 builder (toEncoding.)
+
     1.0.11  Mar 2016
 
         * Updated to GHC 8.0
-
 
     1.0.10  Sep 2015
 
diff --git a/json-autotype.cabal b/json-autotype.cabal
--- a/json-autotype.cabal
+++ b/json-autotype.cabal
@@ -1,6 +1,6 @@
 -- Build information for the package.
 name:                json-autotype
-version:             1.0.11
+version:             1.0.12
 synopsis:            Automatic type declaration for JSON input data
 description:         Generates datatype declarations with Aeson's "FromJSON" instances
                      from a set of example ".json" files.
@@ -34,7 +34,7 @@
 extra-source-files:  README.md changelog.md
 cabal-version:       >=1.10
 bug-reports:         https://github.com/mgajda/json-autotype/issues
-tested-with:         GHC==7.8.4,GHC==7.10.1,GHC==7.6.3
+tested-with:         GHC==7.8.4,GHC==7.10.3,GHC==7.6.3
 
 source-repository head
   type:     git