diff --git XMonad/Hooks/FadeWindows.hs XMonad/Hooks/FadeWindows.hs

index 4b8e62b6..01d06792 100644

--- XMonad/Hooks/FadeWindows.hs

+++ XMonad/Hooks/FadeWindows.hs

@@ -61,7 +61,8 @@ import           Control.Monad.Reader                    (ask

                                                          ,asks)

 import           Control.Monad.State                     (gets)

 import qualified Data.Map                    as M

-import           Data.Monoid

+import           Data.Monoid                      hiding ((<>))

+import           Data.Semigroup

 import           Graphics.X11.Xlib.Extras                (Event(..))

@@ -134,6 +135,9 @@ instance Monoid Opacity where

   r      `mappend` OEmpty = r

   _      `mappend` r      = r

+instance Semigroup Opacity where

+  (<>) = mappend

+

 -- | A FadeHook is similar to a ManageHook, but records window opacity.

 type FadeHook = Query Opacity

diff --git XMonad/Hooks/WallpaperSetter.hs XMonad/Hooks/WallpaperSetter.hs

index 00a3b1c3..d4f5ccb2 100644

--- XMonad/Hooks/WallpaperSetter.hs

+++ XMonad/Hooks/WallpaperSetter.hs

@@ -41,7 +41,8 @@ import Data.Ord (comparing)

 import Control.Monad

 import Control.Applicative

 import Data.Maybe

-import Data.Monoid

+import Data.Monoid hiding ((<>))

+import Data.Semigroup

 -- $usage

 -- This module requires imagemagick and feh to be installed, as these are utilized

@@ -86,6 +87,9 @@ instance Monoid WallpaperList where

   mappend (WallpaperList w1) (WallpaperList w2) =

     WallpaperList $ M.toList $ (M.fromList w2) `M.union` (M.fromList w1)

+instance Semigroup WallpaperList where

+  (<>) = mappend

+

 -- | Complete wallpaper configuration passed to the hook

 data WallpaperConf = WallpaperConf {

     wallpaperBaseDir :: FilePath  -- ^ Where the wallpapers reside (if empty, will look in \~\/.wallpapers/)

diff --git XMonad/Layout/Mosaic.hs XMonad/Layout/Mosaic.hs

index 05655d4c..da44fc50 100644

--- XMonad/Layout/Mosaic.hs

+++ XMonad/Layout/Mosaic.hs

@@ -38,7 +38,8 @@ import Control.Monad(mplus)

 import Data.Foldable(Foldable,foldMap, sum)

 import Data.Function(on)

 import Data.List(sortBy)

-import Data.Monoid(Monoid,mempty, mappend)

+import Data.Monoid(Monoid,mempty, mappend, (<>))

+import Data.Semigroup

 -- $usage

@@ -202,6 +203,9 @@ instance Monoid (Tree a) where

     mappend x Empty = x

     mappend x y = Branch x y

+instance Semigroup (Tree a) where

+    (<>) = mappend

+

 makeTree ::  (Num a1, Ord a1) => (a -> a1) -> [a] -> Tree a

 makeTree _ [] = Empty

 makeTree _ [x] = Leaf x

diff --git xmonad-contrib.cabal xmonad-contrib.cabal

index dde3ccda..c401c6e6 100644

--- xmonad-contrib.cabal

+++ xmonad-contrib.cabal

@@ -36,7 +36,7 @@ cabal-version:      >= 1.6

 build-type:         Simple

 bug-reports:        https://github.com/xmonad/xmonad-contrib/issues

-tested-with: GHC==7.6.3, GHC==7.8.4, GHC==7.10.3, GHC==8.0.1

+tested-with: GHC==7.6.3, GHC==7.8.4, GHC==7.10.3, GHC==8.0.1, GHC==8.2.2, GHC==8.4.1

 source-repository head

   type:     git

@@ -66,7 +66,8 @@ library

                    unix,

                    X11>=1.6.1 && < 1.9,

                    xmonad>=0.13   && < 0.14,

-                   utf8-string

+                   utf8-string,

+                   semigroups

     if flag(use_xft)

         build-depends: X11-xft >= 0.2