diff --git a/map-syntax.cabal b/map-syntax.cabal
--- a/map-syntax.cabal
+++ b/map-syntax.cabal
@@ -1,5 +1,5 @@
 name:           map-syntax
-version:        0.2.0.2
+version:        0.3
 synopsis:       Syntax sugar for defining maps
 description:
     Haskell's canonical list of tuples syntax for defining maps is not very
@@ -13,15 +13,22 @@
 build-type:     Simple
 cabal-version:  >= 1.10
 category:       Data Structures
-Tested-With:    GHC == 7.4.2, GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1
 
+Tested-With:
+  GHC == 7.4.2,
+  GHC == 7.6.3,
+  GHC == 7.8.4,
+  GHC == 7.10.2,
+  GHC == 8.0.1,
+  GHC == 8.2.1,
+  GHC == 8.4.1
+
 extra-source-files:
   .ghci,
   LICENSE,
   README.md,
   runCoverage.sh
 
-
 Library
   hs-source-dirs: src
   default-language: Haskell2010
@@ -29,18 +36,18 @@
   exposed-modules:
     Data.Map.Syntax
 
-
   build-depends:
-    base                       >= 4   && < 5,
+    base                       >= 4.3 && < 4.12,
     containers                 >= 0.3 && < 0.6,
     mtl                        >= 2.0 && < 2.3
 
-  if impl(ghc >= 6.12.0)
-    ghc-options: -Wall -fwarn-tabs -funbox-strict-fields
-                 -fno-warn-unused-do-bind
-  else
-    ghc-options: -Wall -fwarn-tabs -funbox-strict-fields
+  ghc-options: -Wall -fwarn-tabs -funbox-strict-fields -fno-warn-unused-do-bind
 
+  -- See https://ghc.haskell.org/trac/ghc/wiki/Migration/8.0#base-4.9.0.0
+  if impl(ghc >= 8.0)
+    ghc-options: -Wcompat -Wnoncanonical-monad-instances -Wnoncanonical-monadfail-instances
+  else
+    build-depends: semigroups == 0.18.*
 
 source-repository head
   type:     git
@@ -56,12 +63,19 @@
   default-language: Haskell2010
 
   ghc-options: -Wall -fwarn-tabs
+
+  -- See https://ghc.haskell.org/trac/ghc/wiki/Migration/8.0#base-4.9.0.0
+  if impl(ghc >= 8.0)
+    ghc-options: -Wcompat -Wnoncanonical-monad-instances -Wnoncanonical-monadfail-instances
+  else
+    build-depends: semigroups == 0.18.*
+
   build-depends:
-    base                       >= 4        && < 5,
-    containers                 >= 0.3      && < 0.6,
+    base,
+    containers,
     deepseq                    >= 1.3      && < 2,
     HUnit                      >= 1.2      && < 2,
-    mtl                        >= 2.0      && < 2.3,
+    mtl,
     QuickCheck                 >= 2.3.0.2  && < 3,
-    hspec                      >= 2.2.3    && < 2.4,
+    hspec                      >= 2.2.3    && < 2.6,
     transformers               >= 0.3      && < 0.6
diff --git a/src/Data/Map/Syntax.hs b/src/Data/Map/Syntax.hs
--- a/src/Data/Map/Syntax.hs
+++ b/src/Data/Map/Syntax.hs
@@ -52,8 +52,10 @@
 
 #if !MIN_VERSION_base(4,8,0)
 import           Control.Applicative
-import           Data.Monoid
 #endif
+#if !MIN_VERSION_base(4,11,0)
+import           Data.Semigroup
+#endif
 ------------------------------------------------------------------------------
 
 
@@ -92,10 +94,15 @@
 
 
 ------------------------------------------------------------------------------
-instance Monoid (MapSyntax k v) where
-  mempty = return $! ()
-  mappend = (>>)
 
+instance Semigroup (MapSyntax k v) where
+  (<>) = (>>)
+
+instance Monoid (MapSyntax k v) where
+  mempty = pure $! ()
+#if !MIN_VERSION_base(4,11,0)
+  mappend = (<>)
+#endif
 
 ------------------------------------------------------------------------------
 -- | Convenient type alias that will probably be used most of the time.