diff --git a/Data/Compositions/Internal.hs b/Data/Compositions/Internal.hs
--- a/Data/Compositions/Internal.hs
+++ b/Data/Compositions/Internal.hs
@@ -83,6 +83,21 @@
                    , nodeValue :: !a
                    } deriving (Show, Eq, Functor)
 
+#if __GLASGOW_HASKELL__ >= 840
+instance Semigroup a => Semigroup (Compositions a) where
+  (Tree a) <> (Tree b) = Tree (go (reverse a) b)
+    where
+      go [] ys  = ys
+      go ( x : xs) [] = go xs [x]
+      go ( x@(Node sx cx vx) : xs) ( y@(Node sy _ vy) : ys)
+       = case compare sx sy of
+           LT -> go xs (x : y : ys)
+           GT -> let Just (l, r) = cx in go (r : l : xs) (y : ys)
+           EQ -> go (Node (sx + sy) (Just (x, y)) (vx <> vy)  : xs) ys
+
+instance Monoid a => Monoid (Compositions a) where
+  mempty  = Tree []
+#else
 instance (Monoid a) => Monoid (Compositions a) where
   mempty  = Tree []
   mappend (Tree a) (Tree b) = Tree (go (reverse a) b)
@@ -94,6 +109,7 @@
            LT -> go xs (x : y : ys)
            GT -> let Just (l, r) = cx in go (r : l : xs) (y : ys)
            EQ -> go (Node (sx + sy) (Just (x, y)) (vx <> vy)  : xs) ys
+#endif
 
 instance Foldable Compositions where
   foldMap f = foldMap f . concatMap helper . unwrap
diff --git a/Data/Compositions/Snoc/Internal.hs b/Data/Compositions/Snoc/Internal.hs
--- a/Data/Compositions/Snoc/Internal.hs
+++ b/Data/Compositions/Snoc/Internal.hs
@@ -27,9 +27,17 @@
 
 newtype Flip a = Flip { unflip :: a } deriving (Functor, Eq)
 
+#if __GLASGOW_HASKELL__ >= 840
+instance Semigroup a => Semigroup (Flip a) where
+  (Flip a) <> (Flip b) = Flip $ a <> b
+
 instance Monoid a => Monoid (Flip a) where
   mempty = Flip mempty
+#else
+instance Monoid a => Monoid (Flip a) where
+  mempty = Flip mempty
   mappend (Flip a) (Flip b) = Flip (mappend b a)
+#endif
 
 -- | A /compositions list/ or /composition tree/ is a list data type
 -- where the elements are monoids, and the 'mconcat' of any contiguous sublist can be
@@ -57,9 +65,17 @@
 --
 newtype Compositions a = C { unC :: C.Compositions (Flip a) } deriving (Eq)
 
+#if __GLASGOW_HASKELL__ >= 840
+instance Semigroup a => Semigroup (Compositions a) where
+  (C a) <> (C b) = C $ b <> a
+
 instance Monoid a => Monoid (Compositions a) where
+  mempyt = C mempty
+#else
+instance Monoid a => Monoid (Compositions a) where
   mempty = C mempty
   mappend (C a) (C b) = C $ b <> a
+#endif
 
 instance Foldable Compositions where
   foldMap f (C x) = foldMap (f . unflip) . reverse $ toList x
diff --git a/composition-tree.cabal b/composition-tree.cabal
--- a/composition-tree.cabal
+++ b/composition-tree.cabal
@@ -1,5 +1,5 @@
 name:                composition-tree
-version:             0.2.0.3
+version:             0.2.0.4
 synopsis:            Composition trees for arbitrary monoids.
 description:         A compositions list or composition tree is a list data type where the elements are monoids, and the mconcat of any contiguous sublist can be computed in logarithmic time. A common use case of this type is in a wiki, version control system, or collaborative editor, where each change or delta would be stored in a list, and it is sometimes necessary to compute the composed delta between any two versions.
 license:             BSD3
@@ -21,12 +21,12 @@
                        Data.Compositions.Snoc
                        Data.Compositions.Snoc.Internal
   other-extensions:    ScopedTypeVariables, DeriveFunctor, GeneralizedNewtypeDeriving
-  build-depends:       base >=4.7 && <4.10
+  build-depends:       base >=4.7 && <4.12
   default-language:    Haskell2010
 
 
 test-suite             test-comp-tree
   type: exitcode-stdio-1.0
   main-is: tests.hs
-  build-depends: base >= 4.7 && < 4.10, QuickCheck >= 2.7 && < 2.9, composition-tree, doctest >= 0.9 && < 0.12
+  build-depends: base >= 4.7 && < 4.12, QuickCheck >= 2.7 && < 2.12, composition-tree, doctest >= 0.9 && < 0.16
   default-language:    Haskell2010