diff --git a/CHANGES.md b/CHANGES.md
index dddae7f..85652a1 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -18,6 +18,8 @@
     the focus follows when the mouse enters another workspace
     but not moving into any window.
 
+  * Compiles with GHC 8.4.0
+
   * Restored compatability with GHC version prior to 8.0.1 by removing the
     dependency on directory version 1.2.3.
 
diff --git a/src/XMonad/Core.hs b/src/XMonad/Core.hs
index a29818b..ada47bb 100644
--- a/src/XMonad/Core.hs
+++ b/src/XMonad/Core.hs
@@ -39,6 +39,7 @@ import qualified Control.Exception.Extensible as E
 import Control.Applicative
 import Control.Monad.State
 import Control.Monad.Reader
+import Data.Semigroup
 import Data.Default
 import System.FilePath
 import System.IO
@@ -56,7 +57,7 @@ import Graphics.X11.Xlib.Extras (getWindowAttributes, WindowAttributes, Event)
 import Data.Typeable
 import Data.List ((\\))
 import Data.Maybe (isJust,fromMaybe)
-import Data.Monoid
+import Data.Monoid hiding ((<>))
 import System.Environment (lookupEnv)
 
 import qualified Data.Map as M
@@ -152,6 +153,9 @@ instance Applicative X where
   pure = return
   (<*>) = ap
 
+instance Semigroup a => Semigroup (X a) where
+    (<>) = liftM2 (<>)
+
 instance (Monoid a) => Monoid (X a) where
     mempty  = return mempty
     mappend = liftM2 mappend
@@ -166,6 +170,9 @@ newtype Query a = Query (ReaderT Window X a)
 runQuery :: Query a -> Window -> X a
 runQuery (Query m) w = runReaderT m w
 
+instance Semigroup a => Semigroup (Query a) where
+    (<>) = liftM2 (<>)
+
 instance Monoid a => Monoid (Query a) where
     mempty  = return mempty
     mappend = liftM2 mappend
diff --git a/xmonad.cabal b/xmonad.cabal
index b6380ba..f500ae2 100644
--- a/xmonad.cabal
+++ b/xmonad.cabal
@@ -32,7 +32,8 @@ tested-with:
                     GHC==7.6.3,
                     GHC==7.8.4,
                     GHC==7.10.3,
-                    GHC==8.0.1
+                    GHC==8.0.1,
+                    GHC==8.2.2
 
 data-files:         man/xmonad.hs, man/xmonad.1, man/xmonad.1.html
 
@@ -78,7 +79,8 @@ library
                    process,
                    unix,
                    utf8-string >= 0.3 && < 1.1,
-                   X11>=1.8 && < 1.9
+                   X11>=1.8 && < 1.9,
+                   semigroups
 
     if true
         ghc-options:        -funbox-strict-fields -Wall