diff --git a/sql-words.cabal b/sql-words.cabal
--- a/sql-words.cabal
+++ b/sql-words.cabal
@@ -1,5 +1,5 @@
 name:                sql-words
-version:             0.1.5.1
+version:             0.1.6.0
 synopsis:            SQL keywords data constructors into OverloadedString
 description:         This package contiains SQL keywords constructors defined as
                      OverloadedString literals and helper functions to concate these.
@@ -8,11 +8,12 @@
 license-file:        LICENSE
 author:              Kei Hibino
 maintainer:          ex8k.hibino@gmail.com
-copyright:           Copyright (c) 2013-2017 Kei Hibino
+copyright:           Copyright (c) 2013-2018 Kei Hibino
 category:            Database
 build-type:          Simple
 cabal-version:       >=1.10
-tested-with:           GHC == 8.2.1
+tested-with:           GHC == 8.4.1, GHC == 8.4.2
+                     , GHC == 8.2.1, GHC == 8.2.2
                      , GHC == 8.0.1, GHC == 8.0.2
                      , GHC == 7.10.1, GHC == 7.10.2, GHC == 7.10.3
                      , GHC == 7.8.1, GHC == 7.8.2, GHC == 7.8.3, GHC == 7.8.4
@@ -29,6 +30,8 @@
                         Language.SQL.Keyword.Internal.Type
 
   build-depends:          base >=4.5 && <5
+  if impl(ghc < 8)
+    build-depends:        semigroups
   hs-source-dirs:       src
   ghc-options:          -Wall
 
diff --git a/src/Language/SQL/Keyword/Internal/Type.hs b/src/Language/SQL/Keyword/Internal/Type.hs
--- a/src/Language/SQL/Keyword/Internal/Type.hs
+++ b/src/Language/SQL/Keyword/Internal/Type.hs
@@ -1,6 +1,6 @@
 -- |
 -- Module      : Language.SQL.Keyword.Internal.Type
--- Copyright   : 2013 Kei Hibino
+-- Copyright   : 2013-2018 Kei Hibino
 -- License     : BSD3
 --
 -- Maintainer  : ex8k.hibino@gmail.com
@@ -19,7 +19,8 @@
 
 import Data.String (IsString(..))
 import Data.List (find)
-import Data.Monoid (Monoid (..), (<>))
+import Data.Semigroup (Semigroup (..))
+import Data.Monoid (Monoid (..))
 
 
 -- | Diff String type for low-cost concatination.
@@ -46,12 +47,15 @@
 instance Read DString where
   readsPrec _ s = [(dString s, [])]
 
+dappend :: DString -> DString -> DString
+DString f `dappend` DString g = DString $ f . g
+
+instance Semigroup DString where
+  (<>) = dappend
+
 instance Monoid DString where
   mempty  = DString id
-  DString f `mappend` DString g = DString $ f . g
-
-dspace :: DString
-dspace =  dString " "
+  mappend = dappend
 
 -- | Type represent SQL keywords.
 data Keyword = SELECT | ALL | DISTINCT | ON
@@ -130,14 +134,23 @@
    found  Nothing      s = word s
    found (Just (w, _)) _ = w
 
--- | 'Keyword' default concatination separate by space.
-instance Monoid Keyword where
-  mempty  = fromDString mempty
-  a `mappend` b = fromDString $ toDString a `append'` toDString b  where
+kappend :: Keyword -> Keyword -> Keyword
+a `kappend` b = fromDString $ toDString a `append'` toDString b
+  where
     append' p q
       | isEmptyDString p = q
       | isEmptyDString q = p
       | otherwise        = p <> dspace <> q
+    dspace :: DString
+    dspace =  dString " "
+
+instance Semigroup Keyword where
+  (<>) = kappend
+
+-- | 'Keyword' default concatination separate by space.
+instance Monoid Keyword where
+  mempty  = fromDString mempty
+  mappend = kappend
 
 
 -- | Show 'Keyword'