diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,9 @@
+0.8.1
+-----
+* added changelog
+* updated to `transformers` 0.4.1.0
+* added `Data.Functor.Sum` instance for `Unfoldable`
+
+0.8
+---
+* new implementation of `arbitraryDefault`
diff --git a/src/Data/Biunfoldable.hs b/src/Data/Biunfoldable.hs
--- a/src/Data/Biunfoldable.hs
+++ b/src/Data/Biunfoldable.hs
@@ -1,7 +1,7 @@
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Biunfoldable
--- Copyright   :  (c) Sjoerd Visscher 2012
+-- Copyright   :  (c) Sjoerd Visscher 2014
 -- License     :  BSD-style (see the file LICENSE)
 --
 -- Maintainer  :  sjoerd@w3future.com
diff --git a/src/Data/Triunfoldable.hs b/src/Data/Triunfoldable.hs
--- a/src/Data/Triunfoldable.hs
+++ b/src/Data/Triunfoldable.hs
@@ -1,7 +1,7 @@
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Triunfoldable
--- Copyright   :  (c) Sjoerd Visscher 2012
+-- Copyright   :  (c) Sjoerd Visscher 2014
 -- License     :  BSD-style (see the file LICENSE)
 --
 -- Maintainer  :  sjoerd@w3future.com
diff --git a/src/Data/Unfoldable.hs b/src/Data/Unfoldable.hs
--- a/src/Data/Unfoldable.hs
+++ b/src/Data/Unfoldable.hs
@@ -1,7 +1,7 @@
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Unfoldable
--- Copyright   :  (c) Sjoerd Visscher 2012
+-- Copyright   :  (c) Sjoerd Visscher 2014
 -- License     :  BSD-style (see the file LICENSE)
 --
 -- Maintainer  :  sjoerd@w3future.com
@@ -44,6 +44,7 @@
 import Data.Functor.Identity
 import Data.Functor.Product
 import Data.Functor.Reverse
+import Data.Functor.Sum
 import Control.Monad.Trans.State
 import qualified System.Random as R
 import Test.QuickCheck (Arbitrary(..), Gen, sized, resize)
@@ -216,6 +217,12 @@
 instance (Unfoldable p, Unfoldable q) => Unfoldable (Product p q) where
   unfold fa = choose
     [ Pair <$> unfold fa <*> unfold fa ]
+
+instance (Unfoldable p, Unfoldable q) => Unfoldable (Sum p q) where
+  unfold fa = choose
+    [ InL <$> unfold fa
+    , InR <$> unfold fa
+    ]
 
 instance (Unfoldable p, Unfoldable q) => Unfoldable (Compose p q) where
   unfold fa = choose
diff --git a/src/Data/Unfolder.hs b/src/Data/Unfolder.hs
--- a/src/Data/Unfolder.hs
+++ b/src/Data/Unfolder.hs
@@ -1,7 +1,7 @@
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Unfolder
--- Copyright   :  (c) Sjoerd Visscher 2012
+-- Copyright   :  (c) Sjoerd Visscher 2014
 -- License     :  BSD-style (see the file LICENSE)
 --
 -- Maintainer  :  sjoerd@w3future.com
diff --git a/unfoldable.cabal b/unfoldable.cabal
--- a/unfoldable.cabal
+++ b/unfoldable.cabal
@@ -1,5 +1,5 @@
 Name:                 unfoldable
-Version:              0.8
+Version:              0.8.1
 Synopsis:             Class of data structures that can be unfolded.
 Description:          Just as there's a Foldable class, there should also be an Unfoldable class. 
                       .
@@ -23,6 +23,7 @@
 Cabal-version:        >= 1.6
 
 Extra-Source-Files:
+  CHANGELOG.md
   examples/*.hs
   src/Data/Triunfoldable.hs
 
@@ -36,7 +37,7 @@
   
   Build-depends:
       base         >= 4   && < 5 
-    , transformers >= 0.3 && < 0.4
+    , transformers >= 0.4 && < 0.5
     , random       >= 1.0 && < 1.1
     , QuickCheck   >= 2.7.3 && < 2.8