diff --git a/extensible-effects.cabal b/extensible-effects.cabal
--- a/extensible-effects.cabal
+++ b/extensible-effects.cabal
@@ -6,7 +6,7 @@
 -- PVP summary:      +-+------- breaking API changes
 --                   | | +----- non-breaking API additions
 --                   | | | +--- code changes with no API change
-version:             2.5.1.0
+version:             2.5.1.2
 
 -- A short (one-line) description of the package.
 synopsis:            An Alternative to Monad Transformers
@@ -43,7 +43,7 @@
 
 category:            Control, Effect
 
-tested-with:         GHC==8.2.2, GHC==8.0.2, GHC==7.10.3, GHC==7.8.4
+tested-with:         GHC==8.4.1, GHC==8.2.2, GHC==8.0.2, GHC==7.10.3, GHC==7.8.4
 
 build-type:          Simple
 
@@ -134,7 +134,7 @@
      ghc-options:      -Wno-simplifiable-class-constraints
 
   -- Other library packages from which modules are imported.
-  build-depends:       base >= 4.7 && < 4.11
+  build-depends:       base >= 4.7 && < 4.12
                        -- For MonadBase
                ,       transformers-base == 0.4.*
                        -- For MonadBaseControl
@@ -182,7 +182,7 @@
      ghc-options:      -fno-warn-type-defaults -fno-warn-missing-signatures -fno-warn-name-shadowing
 
   build-depends:
-                base >= 4.7 && < 4.11
+                base >= 4.7 && < 4.12
               , QuickCheck
               , HUnit
               , monad-control >= 1.0
@@ -220,7 +220,7 @@
                        -fno-warn-name-shadowing -fno-warn-unused-matches
 
   build-depends:
-                base >= 4.7 && < 4.11
+                base >= 4.7 && < 4.12
               , criterion
               , extensible-effects
               , mtl
diff --git a/src/Control/Eff/Writer/Lazy.hs b/src/Control/Eff/Writer/Lazy.hs
--- a/src/Control/Eff/Writer/Lazy.hs
+++ b/src/Control/Eff/Writer/Lazy.hs
@@ -7,6 +7,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE Safe #-}
+{-# LANGUAGE CPP #-}
 -- | Lazy write-only state
 module Control.Eff.Writer.Lazy ( Writer(..)
                                , tell
@@ -25,7 +26,9 @@
 
 import Control.Monad.Base
 import Control.Monad.Trans.Control
+#if __GLASGOW_HASKELL__ < 804
 import Data.Monoid
+#endif
 
 -- ------------------------------------------------------------------------
 -- | The Writer monad
diff --git a/src/Control/Eff/Writer/Strict.hs b/src/Control/Eff/Writer/Strict.hs
--- a/src/Control/Eff/Writer/Strict.hs
+++ b/src/Control/Eff/Writer/Strict.hs
@@ -8,6 +8,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE Safe #-}
+{-# LANGUAGE CPP #-}
 -- | Strict write-only state
 module Control.Eff.Writer.Strict ( Writer(..)
                                , tell
@@ -26,7 +27,9 @@
 
 import Control.Monad.Base
 import Control.Monad.Trans.Control
+#if __GLASGOW_HASKELL__ < 804
 import Data.Monoid
+#endif
 
 -- ------------------------------------------------------------------------
 -- | The Writer monad