diff --git a/.github/workflows/cabal.project.local b/.github/workflows/cabal.project.local
new file mode 100644
index 0000000..0370cd0
--- /dev/null
+++ b/.github/workflows/cabal.project.local
@@ -0,0 +1,6 @@
+documentation: True
+tests: True
+benchmarks: True
+
+package free-category
+  ghc-options: -j2 -Werror
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
new file mode 100644
index 0000000..b902aee
--- /dev/null
+++ b/.github/workflows/ci.yaml
@@ -0,0 +1,87 @@
+name: Haskell CI
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+
+    defaults:
+      run:
+        shell: bash
+
+    strategy:
+      fail-fast: false
+      matrix:
+        ghc: ["8.8.4", "8.10.7", "9.0.2", "9.2.4", "9.4.2"]
+        os: [ubuntu-latest]
+
+    steps:
+    - name: Install Haskell
+      uses: haskell/actions/setup@v1
+      id: setup-haskell
+      with:
+        ghc-version: ${{ matrix.ghc }}
+        cabal-version: 3.8.1.0
+
+    - name: Select build directory
+      run: |
+        if [ "$RUNNER_OS" == Windows ]; then
+          CABAL_BUILDDIR="D:\\a\\_temp\\dist"
+        else
+          CABAL_BUILDDIR="dist-newstyle"
+        fi
+
+        echo "CABAL_BUILDDIR=$CABAL_BUILDDIR"
+        echo "CABAL_BUILDDIR=$CABAL_BUILDDIR" >> $GITHUB_ENV
+
+    - name: Set cache version
+      run: echo "CACHE_VERSION=9w76Z3Q" >> $GITHUB_ENV
+
+    - name: Set up temp directory
+      env:
+        RUNNER_TEMP: ${{ runner.temp }}
+      run: |
+        echo "TMPDIR=$RUNNER_TEMP"  >> $GITHUB_ENV
+        echo "TMP=$RUNNER_TEMP"     >> $GITHUB_ENV
+
+    - uses: actions/checkout@v3
+
+    - name: Record dependencies
+      id: record-deps
+      run: |
+        cabal build all --dry-run
+        cat dist-newstyle/cache/plan.json | jq -r '."install-plan"[].id' | sort | uniq > dependencies.txt
+
+    - name: Cache `cabal store`
+      uses: actions/cache@v2
+      with:
+        path: ${{ steps.setup-haskell.outputs.cabal-store }}
+        key: cabal-store-${{ env.CACHE_VERSION }}-${{ runner.os }}-${{ matrix.ghc }}-${{ hashFiles('dependencies.txt') }}
+        restore-keys: cabal-store-${{ env.CACHE_VERSION }}-${{ runner.os }}-${{ matrix.ghc }}
+
+    - name: Cache `dist-newstyle`
+      uses: actions/cache@v3
+      with:
+        path: |
+          dist-newstyle
+          !dist-newstyle/**/.git
+        key: cache-dist-${{ env.CACHE_VERSION }}-${{ runner.os }}-${{ matrix.ghc }}
+
+    - name: Use cabal.project.local
+      run: |
+        cat .github/workflows/cabal.project.local >> ./cabal.project.local
+        cat ./cabal.project.local
+
+    - name: Build dependencies
+      run: cabal --builddir="$CABAL_BUILDDIR" build --only-dependencies all
+
+    - name: Build projects [build]
+      run: cabal --builddir="$CABAL_BUILDDIR" build all
+
+    - name: free-category [test]
+      run: cabal --builddir="$CABAL_BUILDDIR" run free-category:test-cats 
+
+    - name: free-category [benchmarks]
+      run: cabal build free-category:benchmarks
+
diff --git a/.github/workflows/posix.yml b/.github/workflows/posix.yml
deleted file mode 100644
index 16da005..0000000
--- a/.github/workflows/posix.yml
+++ /dev/null
@@ -1,32 +0,0 @@
-name: "Haskell/CI"
-on: [push]
-
-jobs:
-  tests:
-    name: "free-category"
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-      - uses: cachix/install-nix-action@v12
-        with:
-          extra_nix_config: |
-            substituters = https://cache.nixos.org https://hydra.iohk.io
-            trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=
-      - name: "cachix"
-        uses: cachix/cachix-action@v8
-        with:
-          name: "free-algebras"
-          signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
-
-      - name: "cachix iohk"
-        run: cachix use iohk
-
-      - name: "[GHC 8.6.5]  free-category"
-        run: |
-          nix-build default.nix --argstr compiler ghc865 -A free-category
-
-      - name: "[GHC 8.8.4]  free-category"
-        run: nix-build default.nix --argstr compiler ghc884 -A free-category
-
-      - name: "[GHC 8.10.4] free-category"
-        run: nix-build default.nix --argstr compiler ghc8104 -A free-category
diff --git a/cabal.project b/cabal.project
index 62f1296..f2d8d02 100644
--- a/cabal.project
+++ b/cabal.project
@@ -1,3 +1,4 @@
-index-state: 2021-03-15T00:00:00Z
-packages: free-category.cabal
-	  examples/examples.cabal
+index-state: 2022-09-06T18:00:00Z
+
+packages: .
+          examples
diff --git a/default.nix b/default.nix
deleted file mode 100644
index 6f00bdd..0000000
--- a/default.nix
+++ /dev/null
@@ -1,41 +0,0 @@
-{ compiler ? "ghc8104"
-}:
-let compiler-nix-name = compiler;
-
-    sources = import ./nix/sources.nix {};
-    iohkNix = import sources.iohk-nix {};
-    haskellNix = import sources."haskell.nix" {};
-    nixpkgs = iohkNix.nixpkgs;
-    haskell-nix = haskellNix.pkgs.haskell-nix;
-
-    # package set
-    pkgs = import nixpkgs
-              { config = haskellNix.config;
-                overlays = [ (_: _: { inherit freeCategoryPackages; }) ];
-              };
-    lib = pkgs.lib;
-
-    # 'cleanGit' cleans a source directory based on the files known by git
-    src = haskell-nix.haskellLib.cleanGit {
-      name = "free-category";
-      src = ./.;
-    };
-
-    # unmodified packages
-    projectPackages = lib.attrNames
-      (haskell-nix.haskellLib.selectProjectPackages
-      (haskell-nix.cabalProject { inherit src compiler-nix-name; }));
-
-    # set GHC options
-    freeCategoryPackages = haskell-nix.cabalProject {
-        inherit src compiler-nix-name;
-        modules =
-          [
-            { packages =
-                lib.genAttrs
-                  projectPackages
-                  (name: { configureFlags = [ "--ghc-option=-Werror" ]; });
-            }
-          ];
-      };
-in pkgs.freeCategoryPackages
diff --git a/free-category.cabal b/free-category.cabal
index 78b9634..4565dc4 100644
--- a/free-category.cabal
+++ b/free-category.cabal
@@ -23,7 +23,7 @@ extra-source-files:
     bench/report-O1.md
     bench/report-O2.md
 stability:      experimental
-tested-with:    GHC==8.6.5, GHC==8.8.4, GHC==8.10.4
+tested-with:    GHC==8.8.4, GHC==8.10.7, GHC==9.0.2, GHC==9.2.4, GHC==9.4.2
 
 source-repository head
   type: git
diff --git a/nix/sources.json b/nix/sources.json
deleted file mode 100644
index 44ccb32..0000000
--- a/nix/sources.json
+++ /dev/null
@@ -1,38 +0,0 @@
-{
-    "haskell.nix": {
-        "branch": "master",
-        "description": "Alternative Haskell Infrastructure for Nixpkgs",
-        "homepage": "https://input-output-hk.github.io/haskell.nix",
-        "owner": "input-output-hk",
-        "repo": "haskell.nix",
-        "rev": "6c9facfada85bd298691ecb2b5b2d124c342f869",
-        "sha256": "07w6wq6rsiq4j26vmi0mvh68wajjj8bd4qjbny2gkdf9jnnf9jj8",
-        "type": "tarball",
-        "url": "https://github.com/input-output-hk/haskell.nix/archive/6c9facfada85bd298691ecb2b5b2d124c342f869.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "iohk-nix": {
-        "branch": "master",
-        "description": "nix scripts shared across projects",
-        "homepage": null,
-        "owner": "input-output-hk",
-        "repo": "iohk-nix",
-        "rev": "bc4216c5b0e14dbde5541763f4952f99c3c712fa",
-        "sha256": "0y5n3limj5dg1vgxyxafg0ky35qq7w97rr00gr3yl16xx5jrhs6w",
-        "type": "tarball",
-        "url": "https://github.com/input-output-hk/iohk-nix/archive/bc4216c5b0e14dbde5541763f4952f99c3c712fa.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "niv": {
-        "branch": "master",
-        "description": "Easy dependency management for Nix projects",
-        "homepage": "https://github.com/nmattia/niv",
-        "owner": "nmattia",
-        "repo": "niv",
-        "rev": "af958e8057f345ee1aca714c1247ef3ba1c15f5e",
-        "sha256": "1qjavxabbrsh73yck5dcq8jggvh3r2jkbr6b5nlz5d9yrqm9255n",
-        "type": "tarball",
-        "url": "https://github.com/nmattia/niv/archive/af958e8057f345ee1aca714c1247ef3ba1c15f5e.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    }
-}
diff --git a/nix/sources.nix b/nix/sources.nix
deleted file mode 100644
index b796fff..0000000
--- a/nix/sources.nix
+++ /dev/null
@@ -1,171 +0,0 @@
-# This file has been generated by Niv.
-
-let
-
-  #
-  # The fetchers. fetch_<type> fetches specs of type <type>.
-  #
-
-  fetch_file = pkgs: name: spec:
-    let
-      name' = sanitizeName name + "-src";
-    in
-      if spec.builtin or true then
-        builtins_fetchurl { inherit (spec) url sha256; name = name'; }
-      else
-        pkgs.fetchurl { inherit (spec) url sha256; name = name'; };
-
-  fetch_tarball = pkgs: name: spec:
-    let
-      name' = sanitizeName name + "-src";
-    in
-      if spec.builtin or true then
-        builtins_fetchTarball { name = name'; inherit (spec) url sha256; }
-      else
-        pkgs.fetchzip { name = name'; inherit (spec) url sha256; };
-
-  fetch_git = name: spec:
-    let
-      ref =
-        if spec ? ref then spec.ref else
-          if spec ? branch then "refs/heads/${spec.branch}" else
-            if spec ? tag then "refs/tags/${spec.tag}" else
-              abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!";
-    in
-      builtins.fetchGit { url = spec.repo; inherit (spec) rev; inherit ref; };
-
-  fetch_local = spec: spec.path;
-
-  fetch_builtin-tarball = name: throw
-    ''[${name}] The niv type "builtin-tarball" is deprecated. You should instead use `builtin = true`.
-        $ niv modify ${name} -a type=tarball -a builtin=true'';
-
-  fetch_builtin-url = name: throw
-    ''[${name}] The niv type "builtin-url" will soon be deprecated. You should instead use `builtin = true`.
-        $ niv modify ${name} -a type=file -a builtin=true'';
-
-  #
-  # Various helpers
-  #
-
-  # https://github.com/NixOS/nixpkgs/pull/83241/files#diff-c6f540a4f3bfa4b0e8b6bafd4cd54e8bR695
-  sanitizeName = name:
-    (
-      concatMapStrings (s: if builtins.isList s then "-" else s)
-        (
-          builtins.split "[^[:alnum:]+._?=-]+"
-            ((x: builtins.elemAt (builtins.match "\\.*(.*)" x) 0) name)
-        )
-    );
-
-  # The set of packages used when specs are fetched using non-builtins.
-  mkPkgs = sources: system:
-    let
-      sourcesNixpkgs =
-        import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) { inherit system; };
-      hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
-      hasThisAsNixpkgsPath = <nixpkgs> == ./.;
-    in
-      if builtins.hasAttr "nixpkgs" sources
-      then sourcesNixpkgs
-      else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
-        import <nixpkgs> {}
-      else
-        abort
-          ''
-            Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
-            add a package called "nixpkgs" to your sources.json.
-          '';
-
-  # The actual fetching function.
-  fetch = pkgs: name: spec:
-
-    if ! builtins.hasAttr "type" spec then
-      abort "ERROR: niv spec ${name} does not have a 'type' attribute"
-    else if spec.type == "file" then fetch_file pkgs name spec
-    else if spec.type == "tarball" then fetch_tarball pkgs name spec
-    else if spec.type == "git" then fetch_git name spec
-    else if spec.type == "local" then fetch_local spec
-    else if spec.type == "builtin-tarball" then fetch_builtin-tarball name
-    else if spec.type == "builtin-url" then fetch_builtin-url name
-    else
-      abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";
-
-  # If the environment variable NIV_OVERRIDE_${name} is set, then use
-  # the path directly as opposed to the fetched source.
-  replace = name: drv:
-    let
-      saneName = stringAsChars (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name;
-      ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
-    in
-      if ersatz == "" then drv else ersatz;
-
-  # Ports of functions for older nix versions
-
-  # a Nix version of mapAttrs if the built-in doesn't exist
-  mapAttrs = builtins.mapAttrs or (
-    f: set: with builtins;
-    listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
-  );
-
-  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/lists.nix#L295
-  range = first: last: if first > last then [] else builtins.genList (n: first + n) (last - first + 1);
-
-  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L257
-  stringToCharacters = s: map (p: builtins.substring p 1 s) (range 0 (builtins.stringLength s - 1));
-
-  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L269
-  stringAsChars = f: s: concatStrings (map f (stringToCharacters s));
-  concatMapStrings = f: list: concatStrings (map f list);
-  concatStrings = builtins.concatStringsSep "";
-
-  # https://github.com/NixOS/nixpkgs/blob/8a9f58a375c401b96da862d969f66429def1d118/lib/attrsets.nix#L331
-  optionalAttrs = cond: as: if cond then as else {};
-
-  # fetchTarball version that is compatible between all the versions of Nix
-  builtins_fetchTarball = { url, name ? null, sha256 }@attrs:
-    let
-      inherit (builtins) lessThan nixVersion fetchTarball;
-    in
-      if lessThan nixVersion "1.12" then
-        fetchTarball ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
-      else
-        fetchTarball attrs;
-
-  # fetchurl version that is compatible between all the versions of Nix
-  builtins_fetchurl = { url, name ? null, sha256 }@attrs:
-    let
-      inherit (builtins) lessThan nixVersion fetchurl;
-    in
-      if lessThan nixVersion "1.12" then
-        fetchurl ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
-      else
-        fetchurl attrs;
-
-  # Create the final "sources" from the config
-  mkSources = config:
-    mapAttrs (
-      name: spec:
-        if builtins.hasAttr "outPath" spec
-        then abort
-          "The values in sources.json should not have an 'outPath' attribute"
-        else
-          spec // { outPath = replace name (fetch config.pkgs name spec); }
-    ) config.sources;
-
-  # The "config" used by the fetchers
-  mkConfig =
-    { sourcesFile ? if builtins.pathExists ./sources.json then ./sources.json else null
-    , sources ? if isNull sourcesFile then {} else builtins.fromJSON (builtins.readFile sourcesFile)
-    , system ? builtins.currentSystem
-    , pkgs ? mkPkgs sources system
-    }: rec {
-      # The sources, i.e. the attribute set of spec name to spec
-      inherit sources;
-
-      # The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers
-      inherit pkgs;
-    };
-
-in
-mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }
diff --git a/src/Control/Arrow/Free.hs b/src/Control/Arrow/Free.hs
index 413cfba..a7e3ad1 100644
--- a/src/Control/Arrow/Free.hs
+++ b/src/Control/Arrow/Free.hs
@@ -37,10 +37,6 @@ module Control.Arrow.Free
 import           Prelude hiding (id, (.))
 import           Control.Arrow (Arrow (..), ArrowChoice (..), (>>>))
 import           Control.Category (Category (..))
-#if __GLASGOW_HASKELL__ < 804
-import           Data.Monoid (Monoid (..))
-import           Data.Semigroup (Semigroup (..))
-#endif
 
 import           Control.Algebra.Free2
   ( AlgebraType0
@@ -97,9 +93,6 @@ instance Semigroup (Arr f o o) where
 
 instance Monoid (Arr f o o) where
     mempty = Id
-#if __GLASGOW_HASKELL__ < 804
-    mappend = (<>)
-#endif
 
 instance Arrow (Arr f) where
   arr       = arrArr
@@ -155,9 +148,6 @@ instance Semigroup (A f o o) where
 
 instance Monoid (A f o o) where
     mempty = id
-#if __GLASGOW_HASKELL__ < 804
-    mappend = (<>)
-#endif
 
 instance Arrow (A f) where
   arr f = A (\_ -> (arr f))
diff --git a/src/Control/Category/Free.hs b/src/Control/Category/Free.hs
index ca55e47..00c3bd8 100644
--- a/src/Control/Category/Free.hs
+++ b/src/Control/Category/Free.hs
@@ -11,20 +11,10 @@
 {-# LANGUAGE TypeOperators         #-}
 {-# LANGUAGE TypeFamilies          #-}
 {-# LANGUAGE ViewPatterns          #-}
-#if __GLASGOW_HASKELL__ >= 806
 {-# LANGUAGE QuantifiedConstraints #-}
-#endif
 
 {-# OPTIONS_HADDOCK show-extensions #-}
 
-#if __GLASGOW_HASKELL__ <= 802
--- ghc802 does not infer that 'cons' is used when using a bidirectional
--- pattern
-{-# OPTIONS_GHC -Wno-unused-top-binds    #-}
--- the 'complete' pragma was introduced in ghc804
-{-# OPTIONS_GHC -Wno-incomplete-patterns #-}
-#endif
-
 module Control.Category.Free
     ( -- * Real time Queue
       Queue (ConsQ, NilQ)
@@ -83,10 +73,6 @@ import           Control.Algebra.Free2
                   , bindFree2
                   )
 import           Control.Arrow (Arrow (..), ArrowZero (..), ArrowChoice (..))
-#if __GLASGOW_HASKELL__ < 804
-import           Data.Monoid (Monoid (..))
-import           Data.Semigroup (Semigroup (..))
-#endif
 import           Data.Kind (Type)
 
 import           Control.Category.Free.Internal
@@ -169,17 +155,10 @@ instance Category (C f) where
   id  = C (\_ -> id)
   (.) = composeC
 
-#if __GLASGOW_HASKELL__ >= 806
 -- | Show instance via 'ListTr'
 --
 instance (forall x y. Show (f x y)) => Show (C f a b) where
     show c = show (hoistFreeH2 c :: ListTr f a b)
-#else
--- | Blind show instance via 'ListTr'
---
-instance Show (C f a b) where
-    show c = show (hoistFreeH2 c :: ListTr f a b)
-#endif
 
 type instance AlgebraType0 C f = ()
 type instance AlgebraType  C c = Category c
@@ -212,6 +191,3 @@ instance Semigroup (C f o o) where
 
 instance Monoid (C f o o) where
   mempty = id
-#if __GLASGOW_HASKELL__ < 804
-  mappend = (<>)
-#endif
diff --git a/src/Control/Category/Free/Internal.hs b/src/Control/Category/Free/Internal.hs
index 0676c79..22d4372 100644
--- a/src/Control/Category/Free/Internal.hs
+++ b/src/Control/Category/Free/Internal.hs
@@ -6,23 +6,12 @@
 {-# LANGUAGE RankNTypes            #-}
 {-# LANGUAGE ScopedTypeVariables   #-}
 {-# LANGUAGE TypeFamilies          #-}
+{-# LANGUAGE TypeOperators         #-}
 {-# LANGUAGE ViewPatterns          #-}
-
-#if __GLASGOW_HASKELL__ >= 806
 {-# LANGUAGE QuantifiedConstraints #-}
-#endif
 
 {-# OPTIONS_HADDOCK show-extensions #-}
 
-#if __GLASGOW_HASKELL__ <= 802
--- ghc802 does not infer that 'consQ' is used when using a bidirectional
--- pattern
-{-# OPTIONS_GHC -Wno-unused-top-binds    #-}
--- the 'complete' pragma was introduced in ghc804
-{-# OPTIONS_GHC -Wno-incomplete-patterns #-}
-#endif
-
-
 -- | Internal module, contains implementation of type aligned real time queues
 -- (C.Okasaki 'Purely Functional Data Structures').
 --
@@ -56,10 +45,6 @@ module Control.Category.Free.Internal
 import           Prelude hiding (id, (.))
 import           Control.Arrow
 import           Control.Category (Category (..))
-#if __GLASGOW_HASKELL__ < 804
-import           Data.Monoid (Monoid (..))
-import           Data.Semigroup (Semigroup (..))
-#endif
 import           Data.Kind (Type)
 
 import           Control.Algebra.Free2 ( AlgebraType0
@@ -95,9 +80,6 @@ instance Category f => Semigroup (Op f o o) where
 
 instance Category f => Monoid (Op f o o) where
     mempty = id
-#if __GLASGOW_HASKELL__ < 804
-    mappend = (<>)
-#endif
 
 
 --
@@ -208,15 +190,9 @@ zipWithL fn queueA queueB = case (queueA, queueB) of
     (ConsTr trA' queueA', ConsTr trB' queueB')
                                  -> ConsTr (trA' `fn` trB') (zipWithL fn queueA' queueB')
 
-#if __GLASGOW_HASKELL__ >= 806
 instance (forall (x :: k) (y :: k). Show (f x y)) => Show (ListTr f a b) where
     show NilTr         = "NilTr"
     show (ConsTr x xs) = "ConsTr " ++ show x ++ " " ++ show xs
-#else
-instance Show (ListTr f a b) where
-    show NilTr         = "NilTr"
-    show (ConsTr _ xs) = "ConsTr _ " ++ show xs
-#endif
 
 instance Category (ListTr f) where
   id  = NilTr
@@ -239,9 +215,6 @@ instance Semigroup (ListTr f o o) where
 
 instance Monoid (ListTr f o o) where
   mempty = NilTr
-#if __GLASGOW_HASKELL__ < 804
-  mappend = (<>)
-#endif
 
 instance Arrow f => Arrow (ListTr f) where
   arr ab                          = arr ab `ConsTr` NilTr
@@ -292,9 +265,7 @@ pattern NilQ :: () => a ~ b => Queue f a b
 pattern NilQ <- (unconsQ -> EmptyL) where
     NilQ = nilQ
 
-#if __GLASGOW_HASKELL__ > 802
 {-# complete NilQ, ConsQ #-}
-#endif
 
 composeQ :: forall k (f :: k -> k -> Type) x y z.
             Queue f y z
@@ -463,7 +434,6 @@ hoistQ nat q = case q of
 
 #-}
 
-#if __GLASGOW_HASKELL__ >= 806
 instance (forall (x :: k) (y :: k). Show (f x y))
       => Show (Queue f a b) where
     show (Queue f r s) =
@@ -473,16 +443,6 @@ instance (forall (x :: k) (y :: k). Show (f x y))
         ++ show r
         ++ ") "
         ++ show (lengthListTr s)
-#else
-instance Show (Queue f r s) where
-    show (Queue f r s) =
-        "Queue "
-      ++ show (lengthListTr f)
-      ++ " "
-      ++ show (lengthListTr r)
-      ++ " "
-      ++ show (lengthListTr s)
-#endif
 
 instance Category (Queue f) where
     id  = NilQ
diff --git a/test/Test/Cat.hs b/test/Test/Cat.hs
index 425eb87..c65a07e 100644
--- a/test/Test/Cat.hs
+++ b/test/Test/Cat.hs
@@ -1,6 +1,9 @@
 {-# LANGUAGE CPP                   #-}
 {-# LANGUAGE DataKinds             #-}
 {-# LANGUAGE FlexibleInstances     #-}
+#if __GLASGOW_HASKELL__ >= 902
+{-# LANGUAGE FlexibleContexts      #-}
+#endif
 {-# LANGUAGE GADTs                 #-}
 {-# LANGUAGE KindSignatures        #-}
 {-# LANGUAGE PolyKinds             #-}
@@ -8,9 +11,7 @@
 {-# LANGUAGE TypeApplications      #-}
 {-# LANGUAGE TupleSections         #-}
 {-# LANGUAGE UndecidableInstances  #-}
-#if __GLASGOW_HASKELL__ >= 806
 {-# LANGUAGE QuantifiedConstraints #-}
-#endif
 
 {-# OPTIONS_GHC -Wno-orphans #-}
 
@@ -19,10 +20,6 @@ module Test.Cat (tests) where
 import           Prelude hiding ((.), id)
 import           Control.Category
 import           Data.Function (on)
-#if __GLASGOW_HASKELL__ < 804
-import           Data.Monoid (Monoid (..))
-import           Data.Semigroup (Semigroup (..))
-#endif
 import           Text.Show.Functions ()
 import           Numeric.Natural (Natural)
 
@@ -173,7 +170,6 @@ genNextTr b = do
 data ArbListTr where
     ArbListTr :: Eq b => ListTr Tr a b -> Sing a -> Sing b -> ArbListTr
 
-#if __GLASGOW_HASKELL__ >= 806
 instance (forall x y. Show (Tr x y)) => Show ArbListTr where
     show (ArbListTr listTr a b) =
          "ArbListTr "
@@ -182,14 +178,6 @@ instance (forall x y. Show (Tr x y)) => Show ArbListTr where
       ++ show b
       ++ " "
       ++ show listTr
-#else
-instance Show ArbListTr where
-    show (ArbListTr _listTr a b) =
-         "ArbListTr "
-      ++ show a
-      ++ " -> "
-      ++ show b
-#endif
 
 instance Arbitrary ArbListTr where
     arbitrary = sized $ \n -> do
@@ -281,9 +269,6 @@ instance Semigroup (IntCat '() '()) where
 
 instance Monoid (IntCat '() '()) where
     mempty = IntCat 0
-#if __GLASGOW_HASKELL__ < 804
-    mappend = (<>)
-#endif
 
 instance Arbitrary (IntCat '() '()) where
     arbitrary = IntCat <$> arbitrary