diff --git a/Data/Aeson/Types.hs b/Data/Aeson/Types.hs
--- a/Data/Aeson/Types.hs
+++ b/Data/Aeson/Types.hs
@@ -14,6 +14,7 @@
     -- * Core JSON types
       Value(..)
     , Encoding
+    , unsafeToEncoding
     , fromEncoding
     , Series
     , Array
diff --git a/Data/Aeson/Types/Instances.hs b/Data/Aeson/Types/Instances.hs
--- a/Data/Aeson/Types/Instances.hs
+++ b/Data/Aeson/Types/Instances.hs
@@ -4,6 +4,11 @@
     ViewPatterns #-}
 {-# LANGUAGE DefaultSignatures #-}
 
+-- Needed for Tagged, Const and Proxy instances
+#if __GLASGOW_HASKELL__ >= 706
+{-# LANGUAGE PolyKinds #-}
+#endif
+
 #define NEEDS_INCOHERENT
 #include "overlapping-compat.h"
 
diff --git a/Data/Aeson/Types/Internal.hs b/Data/Aeson/Types/Internal.hs
--- a/Data/Aeson/Types/Internal.hs
+++ b/Data/Aeson/Types/Internal.hs
@@ -25,6 +25,7 @@
     -- * Core JSON types
       Value(..)
     , Encoding(..)
+    , unsafeToEncoding
     , Series(..)
     , Array
     , emptyArray, isEmptyArray
@@ -343,6 +344,13 @@
       -- ^ Acquire the underlying bytestring builder.
     } deriving (Semigroup,Monoid)
 
+-- | Make Encoding from Builder.
+--
+-- Use with care! You have to make sure that the passed Builder
+-- is a valid JSON Encoding!
+unsafeToEncoding :: Builder -> Encoding
+unsafeToEncoding = Encoding
+
 instance Show Encoding where
     show (Encoding e) = show (toLazyByteString e)
 
@@ -353,7 +361,13 @@
     compare (Encoding a) (Encoding b) =
       compare (toLazyByteString a) (toLazyByteString b)
 
--- | A series of values that, when encoded, should be separated by commas.
+-- | A series of values that, when encoded, should be separated by
+-- commas. Since 0.11.0.0, the '.=' operator is overloaded to create
+-- either @(Text, Value)@ or 'Series'. You can use Series when
+-- encoding directly to a bytestring builder as in the following
+-- example:
+--
+-- > toEncoding (Person name age) = pairs ("name" .= name <> "age" .= age)
 data Series = Empty
             | Value Encoding
             deriving (Typeable)
diff --git a/aeson.cabal b/aeson.cabal
--- a/aeson.cabal
+++ b/aeson.cabal
@@ -1,5 +1,5 @@
 name:            aeson
-version:         0.11.1.4
+version:         0.11.2.0
 license:         BSD3
 license-file:    LICENSE
 category:        Text, Web, JSON
@@ -121,7 +121,6 @@
     build-depends: time >= 1.5
 
   if flag(developer)
-    ghc-options: -Werror
     ghc-prof-options: -auto-all
 
   ghc-options: -O2 -Wall
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,10 @@
 For the latest version of this document, please see [https://github.com/bos/aeson/blob/master/changelog.md](https://github.com/bos/aeson/blob/master/changelog.md).
 
+### 0.11.2.0
+
+* Enable `PolyKinds` to generalize `Proxy`, `Tagged`, and `Const` instances.
+* Add `unsafeToEncoding` in `Data.Aeson.Types`, use with care!
+
 #### 0.11.1.4
 
 * Fix build with `base >= 4.8` and `unordered-containers < 0.2.6`.