diff --git a/ascii-group.cabal b/ascii-group.cabal
--- a/ascii-group.cabal
+++ b/ascii-group.cabal
@@ -1,7 +1,7 @@
 cabal-version: 3.0
 
 name: ascii-group
-version: 1.0.0.15
+version: 1.0.0.16
 synopsis: ASCII character groups
 category: Data, Text
 
@@ -26,15 +26,15 @@
     location: git://github.com/typeclasses/ascii-group.git
 
 common base
-    default-language: Haskell2010
+    default-language: GHC2021
     ghc-options: -Wall
 
     default-extensions:
         NoImplicitPrelude
 
     build-depends:
-        ascii-char ^>= 1.0
-      , base ^>= 4.14 || ^>= 4.15 || ^>= 4.16 || ^>= 4.17
+      , ascii-char ^>= 1.0
+      , base ^>= 4.16 || ^>= 4.17 || ^>= 4.18
 
 library
     import: base
@@ -48,7 +48,7 @@
         StandaloneDeriving
 
     build-depends:
-        hashable ^>= 1.3.5 || ^>= 1.4
+      , hashable ^>= 1.4.2
 
     exposed-modules:
         ASCII.Group
@@ -60,8 +60,8 @@
     main-is: Main.hs
 
     build-depends:
-        ascii-group
-      , hedgehog ^>= 1.0.5 || ^>= 1.1 || ^>= 1.2
+      , ascii-group
+      , hedgehog ^>= 1.1.2 || ^>= 1.2
 
     default-extensions:
         OverloadedStrings
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,7 @@
+### 1.0.0.16 (2023-06-26)
+
+Raise language to GHC2021
+
 ### 1.0.0.15 (2023-01-02)
 
 Minor Cabal correction (change `extra-doc-files` to `extra-source-files`)
diff --git a/library/ASCII/Group.hs b/library/ASCII/Group.hs
--- a/library/ASCII/Group.hs
+++ b/library/ASCII/Group.hs
@@ -1,32 +1,36 @@
-{- |
-
-ASCII characters are broadly categorized into two groups: /control codes/ and /printable characters/.
+-- | ASCII characters are broadly categorized into two groups:
+--   /control codes/ and /printable characters/.
+module ASCII.Group
+  ( -- * The @Group@ type
+    Group (..),
 
--}
+    -- * Functions
+    charGroup,
+    inGroup,
 
-module ASCII.Group
-  (
-    {- * The @Group@ type -} Group (..),
-    {- * Functions -} charGroup, inGroup
-    {- * Notes -} {- $notes -}
+    -- * Notes
+    -- $notes
   )
-  where
+where
 
 import ASCII.Char (Char)
+import ASCII.Char qualified as Char
 import Data.Bool (Bool)
 import Data.Data (Data)
 import Data.Eq (Eq, (==))
 import Data.Hashable (Hashable)
 import Data.Ord (Ord, (<))
 import GHC.Generics (Generic)
-import Prelude (Bounded, Enum)
 import Text.Show (Show)
-
-import qualified ASCII.Char as Char
+import Prelude (Bounded, Enum)
 
-data Group =
-    Control -- ^ 33 of the ASCII characters are /control codes/. A few of these are still in use, but most are obsolete relics of the early days of computing.
-  | Printable -- ^ 95 of the ASCII characters are /printable characters/ such as letters and numbers, mostly corresponding to the keys on an American English keyboard.
+data Group
+  = -- | 33 of the ASCII characters are /control codes/.
+    -- A few of these are still in use, but most are obsolete relics of the early days of computing.
+    Control
+  | -- | 95 of the ASCII characters are /printable characters/ such as letters and numbers,
+    -- mostly corresponding to the keys on an American English keyboard.
+    Printable
 
 deriving stock instance Eq Group
 
@@ -44,63 +48,55 @@
 
 deriving anyclass instance Hashable Group
 
-{- | Determine which group a particular character belongs to.
-
->>> map charGroup [CapitalLetterA,EndOfTransmission]
-[Printable,Control]
-
--}
-
+-- | Determine which group a particular character belongs to
+--
+-- >>> map charGroup [CapitalLetterA,EndOfTransmission]
+-- [Printable,Control]
 charGroup :: Char -> Group
 charGroup x =
-    case x of
-        _ | (x < Char.Space) -> Control
-        Char.Delete          -> Control
-        _                    -> Printable
-
-{- | Test whether a character belongs to a particular group.
-
->>> inGroup Printable EndOfTransmission
-False
-
->>> inGroup Control EndOfTransmission
-True
-
--}
+  case x of
+    _ | (x < Char.Space) -> Control
+    Char.Delete -> Control
+    _ -> Printable
 
+-- | Test whether a character belongs to a particular group
+--
+-- >>> inGroup Printable EndOfTransmission
+-- False
+--
+-- >>> inGroup Control EndOfTransmission
+-- True
 inGroup :: Group -> Char -> Bool
 inGroup g x = charGroup x == g
 
-{- $notes
-
-Space is a printable character (perhaps surprisingly, given that it is invisible).
-
->>> charGroup Space
-Printable
-
-Tab is a control code (perhaps surprisingly, given that space is a printable character).
-
->>> charGroup HorizontalTab
-Control
-
-A few examples of printable characters:
-
->>> all (inGroup Printable) [CapitalLetterA,SmallLetterZ,Digit4,Tilde]
-True
-
-A few examples of control characters:
-
->>> all (inGroup Control) [Null,Substitute,UnitSeparator,Delete]
-True
-
-There are 33 control codes.
-
->>> length (filter (inGroup Control) allCharacters)
-33
-
-There are 95 printable characters.
-
->>> length (filter (inGroup Printable) allCharacters)
-95
-
--}
+-- $notes
+--
+-- Space is a printable character (perhaps surprisingly, given that it is invisible).
+--
+-- >>> charGroup Space
+-- Printable
+--
+-- Tab is a control code (perhaps surprisingly, given that space is a printable character).
+--
+-- >>> charGroup HorizontalTab
+-- Control
+--
+-- A few examples of printable characters:
+--
+-- >>> all (inGroup Printable) [CapitalLetterA,SmallLetterZ,Digit4,Tilde]
+-- True
+--
+-- A few examples of control characters:
+--
+-- >>> all (inGroup Control) [Null,Substitute,UnitSeparator,Delete]
+-- True
+--
+-- There are 33 control codes.
+--
+-- >>> length (filter (inGroup Control) allCharacters)
+-- 33
+--
+-- There are 95 printable characters.
+--
+-- >>> length (filter (inGroup Printable) allCharacters)
+-- 95
diff --git a/test/Main.hs b/test/Main.hs
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -1,64 +1,92 @@
 module Main (main) where
 
-import ASCII.Group
-
 import ASCII.Char (Char (..), allCharacters)
-
-import Control.Monad (Monad (..))
+import ASCII.Group
+import Control.Monad (Monad (..), when)
 import Data.Bool (not)
 import Data.Foldable (all)
 import Data.Function (($))
 import Data.List (filter, length)
-import System.IO (IO)
-import Control.Monad (when)
+import Hedgehog
+  ( Property,
+    assert,
+    checkParallel,
+    discover,
+    property,
+    withTests,
+    (===),
+  )
 import System.Exit (exitFailure)
-
-import Hedgehog (Property, assert, checkParallel, discover, property,
-                 withTests, (===))
+import System.IO (IO)
 
 main :: IO ()
 main = checkParallel $$(discover) >>= \ok -> when (not ok) exitFailure
 
 prop_letter :: Property
-prop_letter = withTests 1 $ property $
-    charGroup CapitalLetterA === Printable
+prop_letter =
+  withTests 1 $
+    property $
+      charGroup CapitalLetterA === Printable
 
 prop_control :: Property
-prop_control = withTests 1 $ property $
-    charGroup EndOfTransmission === Control
+prop_control =
+  withTests 1 $
+    property $
+      charGroup EndOfTransmission === Control
 
 prop_not_printable :: Property
-prop_not_printable = withTests 1 $ property $
-    assert $ not $ inGroup Printable EndOfTransmission
+prop_not_printable =
+  withTests 1 $
+    property $
+      assert $
+        not $
+          inGroup Printable EndOfTransmission
 
 prop_is_control :: Property
-prop_is_control = withTests 1 $ property $
-    assert $ inGroup Control EndOfTransmission
+prop_is_control =
+  withTests 1 $
+    property $
+      assert $
+        inGroup Control EndOfTransmission
 
 -- It is perhaps surprising that space is considered a
 -- "printable" character, since it does not visibly appear.
 prop_space_is_printable :: Property
-prop_space_is_printable = withTests 1 $ property $
-    charGroup Space === Printable
+prop_space_is_printable =
+  withTests 1 $
+    property $
+      charGroup Space === Printable
 
 -- It is perhaps surprising that horizontal tab is not
 -- in the same category as space.
 prop_horizontal_tab_is_control :: Property
-prop_horizontal_tab_is_control = withTests 1 $ property $
-    charGroup HorizontalTab === Control
+prop_horizontal_tab_is_control =
+  withTests 1 $
+    property $
+      charGroup HorizontalTab === Control
 
 prop_various_printables :: Property
-prop_various_printables = withTests 1 $ property $
-    assert $ all (inGroup Printable) [CapitalLetterA, SmallLetterZ, Digit4, Tilde]
+prop_various_printables =
+  withTests 1 $
+    property $
+      assert $
+        all (inGroup Printable) [CapitalLetterA, SmallLetterZ, Digit4, Tilde]
 
 prop_various_controls :: Property
-prop_various_controls = withTests 1 $ property $
-    assert $ all (inGroup Control) [Null, Substitute, UnitSeparator, Delete]
+prop_various_controls =
+  withTests 1 $
+    property $
+      assert $
+        all (inGroup Control) [Null, Substitute, UnitSeparator, Delete]
 
 prop_count_printables :: Property
-prop_count_printables = withTests 1 $ property $
-    length (filter (inGroup Printable) allCharacters) === 95
+prop_count_printables =
+  withTests 1 $
+    property $
+      length (filter (inGroup Printable) allCharacters) === 95
 
 prop_count_controls :: Property
-prop_count_controls = withTests 1 $ property $
-    length (filter (inGroup Control) allCharacters) === 33
+prop_count_controls =
+  withTests 1 $
+    property $
+      length (filter (inGroup Control) allCharacters) === 33