diff --git a/CHANGES.md b/CHANGES.md
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,8 @@
+0.3.4.0 (2018-11-11)
+====================
+
+-   Support GHC 8.6 (#20).
+
 0.3.3.0 (2018-06-15)
 ====================
 
diff --git a/pinch.cabal b/pinch.cabal
--- a/pinch.cabal
+++ b/pinch.cabal
@@ -2,10 +2,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 81e0ecf2f54c375e7fea61c471bd14781b8d75e4df2e4275e35022d78671ba9e
+-- hash: 58647b3d18496665a01f919c63779068ca00ad1c2ea6eaddba33eedf9fc712d2
 
 name:           pinch
-version:        0.3.3.0
+version:        0.3.4.0
 cabal-version:  >= 1.10
 build-type:     Simple
 license:        BSD3
diff --git a/src/Pinch/Internal/Generic.hs b/src/Pinch/Internal/Generic.hs
--- a/src/Pinch/Internal/Generic.hs
+++ b/src/Pinch/Internal/Generic.hs
@@ -13,6 +13,7 @@
 {-# LANGUAGE ScopedTypeVariables        #-}
 {-# LANGUAGE TypeFamilies               #-}
 {-# LANGUAGE TypeOperators              #-}
+{-# LANGUAGE UndecidableInstances       #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 #if __GLASGOW_HASKELL__ < 709