diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,8 @@
 # Changelog for free-algebras
 
+## Version 0.1.0.2
+- Support `GHC-9.0`, `GHC-9.2` and `GHC-9.4`, drop support for `GHC-8.6` or earlier.
+
 ## Version 0.0.8.0
 - Added two properties for each: `foldMapFree`, `foldNatFree` and
   `foldNatFree2`.
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # Free Algebras
 [![Maintainer: coot](https://img.shields.io/badge/maintainer-coot-lightgrey.svg)](http://github.com/coot)
-[![CircleCI](https://circleci.com/gh/coot/free-algebras/tree/master.svg?style=svg)](https://circleci.com/gh/coot/free-algebras/tree/master)
+[![POSIX](https://github.com/coot/free-algebras/actions/workflows/posix.yml/badge.svg)](https://github.com/coot/free-algebras/actions/workflows/posix.yml)
 
 Universal algebra approach (which is compatible with categorical approach) to
 free algebras (including higher order structures like functors, applicative
diff --git a/free-algebras.cabal b/free-algebras.cabal
--- a/free-algebras.cabal
+++ b/free-algebras.cabal
@@ -1,6 +1,6 @@
 cabal-version:  2.2
 name:           free-algebras
-version:        0.1.0.1
+version:        0.1.0.2
 synopsis:       Free algebras
 description:
   Algebraic approach to free algebras, inspired by Univeral Algebra and
@@ -19,7 +19,7 @@
     ChangeLog.md
     README.md
 stability:      experimental
-tested-with:    GHC==8.6.5, GHC==8.8.4, GHC==8.10.4
+tested-with:    GHC==8.8.4, GHC==8.10.4, GHC==9.0.2, GHC==9.2.4, GHC==9.4.2
 
 source-repository head
   type: git
@@ -57,7 +57,7 @@
     , free            >= 4.0 && <6.0
     , groups          >= 0.3 && <0.6
     , kan-extensions  >= 4.1 && <6.0
-    , mtl             >= 2.2 && <2.3
+    , mtl             >= 2.2 && <2.4
     , transformers    >= 0.5 && <0.6
   default-language: Haskell2010
 
@@ -92,7 +92,7 @@
     , dlist
     , free
     , groups
-    , hedgehog       >= 0.6 && < 1.1
+    , hedgehog       >= 0.6 && < 1.3
     , kan-extensions
     , mtl
     , transformers
diff --git a/src/Control/Algebra/Free.hs b/src/Control/Algebra/Free.hs
--- a/src/Control/Algebra/Free.hs
+++ b/src/Control/Algebra/Free.hs
@@ -13,10 +13,8 @@
 {-# LANGUAGE ScopedTypeVariables        #-}
 {-# LANGUAGE TypeFamilies               #-}
 {-# LANGUAGE TypeOperators              #-}
-#if __GLASGOW_HASKELL__ >= 806
 {-# LANGUAGE QuantifiedConstraints      #-}
 {-# LANGUAGE UndecidableInstances       #-}
-#endif
 
 -- 'ListT' transformer is depreciated
 {-# OPTIONS_GHC -Wno-deprecations       #-}
@@ -54,9 +52,7 @@
     ) where
 
 import           Control.Applicative ( Alternative (..)
-#if __GLASGOW_HASKELL__ >= 806
                                      , liftA2
-#endif
                                      )
 import           Control.Applicative.Free (Ap)
 import qualified Control.Applicative.Free as Ap
@@ -64,11 +60,7 @@
 import qualified Control.Applicative.Free.Final as Final
 import           Control.Alternative.Free (Alt (..))
 import qualified Control.Alternative.Free as Alt
-#if __GLASGOW_HASKELL__ >= 806
 import           Control.Monad ( MonadPlus (..), foldM, join)
-#else
-import           Control.Monad (                 foldM, join)
-#endif
 import           Control.Monad.Except (ExceptT (..), MonadError (..))
 import           Control.Monad.Free (Free)
 import qualified Control.Monad.Free as Free
@@ -86,9 +78,7 @@
 import           Control.Monad.Writer.Class (MonadWriter (..))
 import qualified Control.Monad.Writer.Lazy as L (WriterT (..))
 import qualified Control.Monad.Writer.Strict as S (WriterT (..))
-#if __GLASGOW_HASKELL__ >= 806
 import           Control.Monad.Zip (MonadZip (..))
-#endif
 import           Data.Kind (Constraint, Type)
 import           Data.Fix (Fix, cataM)
 import           Data.Functor.Coyoneda (Coyoneda (..), liftCoyoneda)
@@ -216,7 +206,7 @@
 
 -- | @'unFoldNatFree'@ is an inverse of @'foldNatFree'@
 --
--- It is uniquelly determined by its universal property (by Yonneda lemma):
+-- It is uniquely determined by its universal property (by Yonneda lemma):
 --
 -- prop> unFoldNatFree id = ruturnFree1
 --
@@ -609,7 +599,6 @@
           runFree1 :: forall g. c g => (forall x. f x -> g x) -> g a
         }
 
-#if __GLASGOW_HASKELL__ >= 806
 --
 -- instances for @'Free1'@ using quantified constraints
 --
@@ -651,13 +640,7 @@
     Free1 f >>= k = Free1 $ \h ->
         f h >>= (\a -> case k a of Free1 l -> l h)
 
-    Free1 f >> Free1 g = Free1 $ \h -> f h >> g h
 
-#if __GLASGOW_HASKELL__ < 808
-    fail s = Free1 $ \_ -> fail s
-#endif
-
-
 instance (forall h. c h => Alternative h, c (Free1 c f))
          => Alternative (Free1 c f) where
     empty = Free1 $ \_ -> empty
@@ -694,8 +677,6 @@
     liftFree = \fa -> Free1 $ \g -> g fa
 
     foldNatFree nat (Free1 f) = f nat
-
-#endif
 
 -- $monadContT
 --
diff --git a/src/Data/Algebra/Free.hs b/src/Data/Algebra/Free.hs
--- a/src/Data/Algebra/Free.hs
+++ b/src/Data/Algebra/Free.hs
@@ -38,9 +38,6 @@
 
 import           Prelude
 
-#if __GLASGOW_HASKELL__ < 808
-import           Data.DList (DList)
-#endif
 import           Data.DList as DList
 import           Data.Functor.Identity (Identity (..))
 #if MIN_VERSION_data_fix(0,3,0)
@@ -52,16 +49,7 @@
 import           Data.Kind (Constraint, Type)
 import           Data.List.NonEmpty (NonEmpty (..))
 import qualified Data.List.NonEmpty as NonEmpty
-import           Data.Monoid ( Endo (..)
-#if __GLASGOW_HASKELL__ < 808
-                             , Monoid (..)
-#endif
-                             , Dual (..))
-#if __GLASGOW_HASKELL__ < 808
-import           Data.Semigroup ( Semigroup
-                                , (<>)
-                                )
-#endif
+import           Data.Monoid (Endo (..), Dual (..))
 import           Data.Algebra.Pointed (Pointed (..))
 
 --
@@ -144,7 +132,7 @@
 
 -- | Inverse of @'foldMapFree'@
 --
--- It is uniquelly determined by its universal property (by Yonneda lemma):
+-- It is uniquely determined by its universal property (by Yonneda lemma):
 --
 -- prop> unFoldMapFree id = returnFree
 --
diff --git a/src/Data/Group/Free.hs b/src/Data/Group/Free.hs
--- a/src/Data/Group/Free.hs
+++ b/src/Data/Group/Free.hs
@@ -30,9 +30,6 @@
 #endif
 import           Data.Group (Group (..))
 import           Data.List (foldl')
-#if __GLASGOW_HASKELL__ < 808
-import           Data.Semigroup (Semigroup (..))
-#endif
 
 import           Data.Algebra.Free
                     ( AlgebraType
@@ -62,11 +59,11 @@
     fmap f (FreeGroup as) = FreeGroup $ bimap f f <$> as
 
 instance Applicative FreeGroup where
-    pure  = return
+    pure a = FreeGroup $ DList.singleton (Right a)
     (<*>) = ap
 
 instance Monad FreeGroup where
-    return a           = FreeGroup $ DList.singleton (Right a)
+    return  = pure
     FreeGroup as >>= f = FreeGroup $ as >>= runFreeGroup . either f f
 
 -- | Normalize a @Dlist@, i.e. remove adjacent inverses from a word, i.e.
diff --git a/src/Data/Semigroup/Abelian.hs b/src/Data/Semigroup/Abelian.hs
--- a/src/Data/Semigroup/Abelian.hs
+++ b/src/Data/Semigroup/Abelian.hs
@@ -1,6 +1,9 @@
 {-# LANGUAGE CPP          #-}
 {-# LANGUAGE TypeFamilies #-}
 
+-- 'Option' will be removed in 'ghc-9.2'.
+{-# OPTIONS_GHC -Wno-deprecations #-}
+
 module Data.Semigroup.Abelian
     ( AbelianSemigroup
     , FreeAbelianSemigroup
@@ -14,19 +17,15 @@
 import           Data.Map (Map)
 import qualified Data.Map as Map
 import           Data.Set (Set)
-#if __GLASGOW_HASKELL__ < 808
 import           Data.Semigroup
-                    ( Semigroup (..),
-#else
-import           Data.Semigroup
-                    (
-#endif
-                      All
+                    ( All
                     , Any
                     , Dual
                     , Max
                     , Min
+#if __GLASGOW_HASKELL__ < 902
                     , Option
+#endif
                     , Product
                     , Sum
                     )
@@ -60,9 +59,8 @@
 
 instance Ord a => AbelianSemigroup (Min a)
 
-#if __GLASGOW_HASKELL__ >= 900
 instance AbelianSemigroup a => AbelianSemigroup (Maybe a)
-#else
+#if __GLASGOW_HASKELL__ < 902
 instance AbelianSemigroup a => AbelianSemigroup (Option a)
 #endif
 
diff --git a/src/Data/Semigroup/Semilattice.hs b/src/Data/Semigroup/Semilattice.hs
--- a/src/Data/Semigroup/Semilattice.hs
+++ b/src/Data/Semigroup/Semilattice.hs
@@ -13,9 +13,6 @@
 import           Data.IntSet (IntSet)
 import           Data.Semigroup ( All
                                 , Any
-#if __GLASGOW_HASKELL__ < 808
-                                , Semigroup
-#endif
                                 , sconcat)
 import           Data.Set (Set)
 import qualified Data.Set as Set