diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,9 @@
+5.0.1
+-------
+* `transformers-compat` 0.5 support
+* Removed some redundant constraints.
+* GHC 8 support
+
 5.0.0.4
 -------
 * `doctest` 0.10 support
diff --git a/semigroupoids.cabal b/semigroupoids.cabal
--- a/semigroupoids.cabal
+++ b/semigroupoids.cabal
@@ -1,6 +1,6 @@
 name:          semigroupoids
 category:      Control, Comonads
-version:       5.0.0.4
+version:       5.0.1
 license:       BSD3
 cabal-version: >= 1.8
 license-file:  LICENSE
@@ -119,7 +119,7 @@
     bifunctors          >= 5       && < 6,
     semigroups          >= 0.8.3.1 && < 1,
     transformers        >= 0.2     && < 0.6,
-    transformers-compat >= 0.3     && < 0.5
+    transformers-compat >= 0.3     && < 0.6
 
   if flag(containers)
     build-depends: containers >= 0.3 && < 0.6
diff --git a/src/Data/Functor/Bind/Trans.hs b/src/Data/Functor/Bind/Trans.hs
--- a/src/Data/Functor/Bind/Trans.hs
+++ b/src/Data/Functor/Bind/Trans.hs
@@ -46,10 +46,10 @@
 instance BindTrans (ReaderT e) where
   liftB = ReaderT . const
 
-instance (Semigroup w, Monoid w) => BindTrans (Lazy.WriterT w) where
+instance Monoid w => BindTrans (Lazy.WriterT w) where
   liftB = Lazy.WriterT . fmap (\a -> (a, mempty))
 
-instance (Semigroup w, Monoid w) => BindTrans (Strict.WriterT w) where
+instance Monoid w => BindTrans (Strict.WriterT w) where
   liftB = Strict.WriterT . fmap (\a -> (a, mempty))
 
 instance BindTrans (Lazy.StateT s) where
@@ -58,10 +58,10 @@
 instance BindTrans (Strict.StateT s) where
   liftB m = Strict.StateT $ \s -> fmap (\a -> (a, s)) m
 
-instance (Semigroup w, Monoid w) => BindTrans (Lazy.RWST r w s) where
+instance Monoid w => BindTrans (Lazy.RWST r w s) where
   liftB m = Lazy.RWST $ \ _r s -> fmap (\a -> (a, s, mempty)) m
 
-instance (Semigroup w, Monoid w) => BindTrans (Strict.RWST r w s) where
+instance Monoid w => BindTrans (Strict.RWST r w s) where
   liftB m = Strict.RWST $ \ _r s -> fmap (\a -> (a, s, mempty)) m
 
 instance BindTrans (ContT r) where
diff --git a/src/Data/Functor/Extend.hs b/src/Data/Functor/Extend.hs
--- a/src/Data/Functor/Extend.hs
+++ b/src/Data/Functor/Extend.hs
@@ -24,7 +24,8 @@
 import Control.Category
 import Control.Monad.Trans.Identity
 import Data.Functor.Identity
-import Data.Semigroup
+import Data.Functor.Sum (Sum(..))
+import Data.Semigroup (Semigroup(..))
 import Data.List (tails)
 import Data.List.NonEmpty (NonEmpty(..), toList)
 
@@ -36,7 +37,6 @@
 
 
 #ifdef MIN_VERSION_comonad
-import Data.Functor.Coproduct
 import Control.Comonad.Trans.Env
 import Control.Comonad.Trans.Store
 import Control.Comonad.Trans.Traced
@@ -95,10 +95,12 @@
 #endif
 
 #ifdef MIN_VERSION_comonad
+{-
 instance (Extend f, Extend g) => Extend (Coproduct f g) where
   extended f = Coproduct . coproduct
     (Left . extended (f . Coproduct . Left))
     (Right . extended (f . Coproduct . Right))
+-}
 
 instance Extend w => Extend (EnvT e w) where
   duplicated (EnvT e wa) = EnvT e (extended (EnvT e) wa)
@@ -132,6 +134,10 @@
   extended f w@ ~(_ :| aas) = f w :| case aas of
       []     -> []
       (a:as) -> toList (extended f (a :| as))
+
+instance (Extend f, Extend g) => Extend (Sum f g) where
+  extended f (InL l) = InL (extended (f . InL) l)
+  extended f (InR r) = InR (extended (f . InR) r)
 
 -- $definition
 -- There are two ways to define an 'Extend' instance:
diff --git a/src/Data/Semigroup/Foldable/Class.hs b/src/Data/Semigroup/Foldable/Class.hs
--- a/src/Data/Semigroup/Foldable/Class.hs
+++ b/src/Data/Semigroup/Foldable/Class.hs
@@ -35,10 +35,6 @@
 import Data.Foldable
 import Data.Functor.Compose
 
-#ifdef MIN_VERSION_comonad
-import Data.Functor.Coproduct
-#endif
-
 import Data.Functor.Identity
 import Data.Functor.Product as Functor
 import Data.Functor.Reverse
@@ -167,11 +163,6 @@
 instance (Foldable1 f, Foldable1 g) => Foldable1 (Sum f g) where
   foldMap1 f (InL x) = foldMap1 f x
   foldMap1 f (InR y) = foldMap1 f y
-
-#ifdef MIN_VERSION_comonad
-instance (Foldable1 f, Foldable1 g) => Foldable1 (Coproduct f g) where
-  foldMap1 f = coproduct (foldMap1 f) (foldMap1 f)
-#endif
 
 instance Foldable1 NonEmpty where
   foldMap1 f (a :| []) = f a
diff --git a/src/Data/Semigroup/Traversable/Class.hs b/src/Data/Semigroup/Traversable/Class.hs
--- a/src/Data/Semigroup/Traversable/Class.hs
+++ b/src/Data/Semigroup/Traversable/Class.hs
@@ -31,10 +31,6 @@
 import Data.Functor.Apply
 import Data.Functor.Compose
 
-#ifdef MIN_VERSION_comonad
-import Data.Functor.Coproduct as Functor
-#endif
-
 import Data.Functor.Identity
 import Data.Functor.Product as Functor
 import Data.Functor.Reverse
@@ -170,13 +166,6 @@
 instance (Traversable1 f, Traversable1 g) => Traversable1 (Functor.Sum f g) where
   traverse1 f (Functor.InL x) = Functor.InL <$> traverse1 f x
   traverse1 f (Functor.InR y) = Functor.InR <$> traverse1 f y
-
-#ifdef MIN_VERSION_comonad
-instance (Traversable1 f, Traversable1 g) => Traversable1 (Coproduct f g) where
-  traverse1 f = coproduct
-    (fmap (Coproduct . Left) . traverse1 f)
-    (fmap (Coproduct . Right) . traverse1 f)
-#endif
 
 #ifdef MIN_VERSION_containers
 instance Traversable1 Tree where