diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+# 0.9.2.1
+
+- No external changes.
+- Use cabal-docspec instead of doctest
+
 # 0.9.2.0
 
 - Add instance of `Bounded` for `FiniteEnumeration` (the same as `Generically`)
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -38,7 +38,7 @@
 import Data.Semigroup (Semigroup(..))
 
 -- generic-data
-import Generic.Data (gmappend)
+import Generic.Data (Generic, gmappend)
 import Generic.Data.Orphans ()
 ```
 
diff --git a/Setup.hs b/Setup.hs
--- a/Setup.hs
+++ b/Setup.hs
@@ -1,2 +1,2 @@
-import Distribution.Extra.Doctest (defaultMainWithDoctests)
-main = defaultMainWithDoctests "generic-data-doctest"
+import Distribution.Simple
+main = defaultMain
diff --git a/generic-data.cabal b/generic-data.cabal
--- a/generic-data.cabal
+++ b/generic-data.cabal
@@ -1,5 +1,5 @@
 name:                generic-data
-version:             0.9.2.0
+version:             0.9.2.1
 synopsis:            Deriving instances with GHC.Generics and related utilities
 description:
   Generic implementations of standard type classes.
@@ -12,16 +12,12 @@
 maintainer:          lysxia@gmail.com
 copyright:           2018-2020 Li-yao Xia
 category:            Generics
-build-type:          Custom
+build-type:          Simple
 extra-source-files:  README.md, CHANGELOG.md
 cabal-version:       >=1.10
 tested-with:         GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.3, GHC == 8.6.1,
                      GHC == 8.6.3, GHC == 8.6.5, GHC == 8.8.2
 
-custom-setup
-  setup-depends:
-    base, Cabal, cabal-doctest >= 1.0.6 && < 1.1
-
 library
   hs-source-dirs:      src
   exposed-modules:
@@ -143,20 +139,6 @@
   default-language: Haskell2010
   type: exitcode-stdio-1.0
   if impl(ghc < 8.2) || os(windows)
-    buildable: False
-
-test-suite generic-data-doctest
-  hs-source-dirs: test
-  main-is: doctest.hs
-  build-depends:
-    doctest,
-    QuickCheck,
-    generic-data,
-    base
-  ghc-options: -Wall
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  if !impl(ghc >= 8.6)
     buildable: False
 
 benchmark bench
diff --git a/src/Generic/Data/Internal/Enum.hs b/src/Generic/Data/Internal/Enum.hs
--- a/src/Generic/Data/Internal/Enum.hs
+++ b/src/Generic/Data/Internal/Enum.hs
@@ -253,26 +253,26 @@
 
 -- | Extends the 'StandardEnum' option for 'GEnum' to allow all constructors to 
 -- have arbitrary many fields. Each field type must be an instance of 
--- both 'Enum' and 'Bounded'.
+-- both 'Enum' and 'Bounded'. Avoid fields of types 'Int' and 'Word'.
 --
 -- === __Details__
 --
--- Two restrictions require the user's caution:
+-- Two restrictions require the user's attention:
 --
 -- * The 'Enum' instances of the field types need to start enumerating from 0. 
--- Particularly 'Int' is an unfit field type, because the enumeration of the 
+-- In particular, 'Int' is an unfit field type, because the enumeration of the
 -- negative values starts before 0. 
 --
 -- * There can only be up to @'maxBound' :: 'Int'@ values (because the implementation
 -- represents the cardinality explicitly as an 'Int'). This restriction makes
--- 'Word' an invalid field type. Notably, it is insufficient for each
+-- 'Word' an invalid field type as well. Notably, it is insufficient for each
 -- individual field types to stay below this limit. Instead it applies to the
 -- generic type as a whole.
 --
--- The resulting 'GEnum' instance starts enumerating from @0@ up to
--- @(cardinality - 1)@ and respects the generic 'Ord' instance (defined by
--- 'Generic.Data.gcompare'). The values from different constructors are enumerated
--- sequentially; they are not interleaved.
+-- Elements are numbered by 'toEnum', from @0@ up to @(cardinality - 1)@.
+-- The resulting ordering matches the generic 'Ord' instance defined by
+-- 'Generic.Data.gcompare'.
+-- The values from different constructors are enumerated sequentially.
 --
 -- @
 -- data Example = C0 Bool Bool | C1 Bool
diff --git a/src/Generic/Data/Internal/Generically.hs b/src/Generic/Data/Internal/Generically.hs
--- a/src/Generic/Data/Internal/Generically.hs
+++ b/src/Generic/Data/Internal/Generically.hs
@@ -31,13 +31,16 @@
 import Generic.Data.Internal.Show
 import Generic.Data.Internal.Traversable (GFoldable, GTraversable, gfoldMap, gtraverse, gsequenceA)
 
+-- $setup
+-- >>> :set -XDerivingVia -XDeriveGeneric
+-- >>> import GHC.Generics (Generic, Generic1)
+
 -- | Type with instances derived via 'Generic'.
 --
 -- === Examples
 --
 -- ==== __Deriving 'Eq', 'Ord', 'Show', 'Read'__
 --
--- >>> :set -XDerivingVia -XDeriveGeneric
 -- >>> :{
 -- data T = C Int Bool
 --   deriving Generic
@@ -48,6 +51,7 @@
 --
 -- The type must have only one constructor.
 --
+-- >>> import Data.Monoid (Sum)
 -- >>> :{
 -- data U = D [Int] (Sum Int)
 --   deriving Generic
@@ -164,6 +168,7 @@
 --   deriving (Functor, Applicative) via (Generically1 G)
 -- :}
 --
+-- >>> import Control.Applicative (Alternative)
 -- >>> :{
 -- data G' a = G' (Maybe a) [a]
 --   deriving Generic1
@@ -184,6 +189,7 @@
 --
 -- ==== __Deriving 'Eq1', 'Ord1'__
 --
+-- >>> import Data.Functor.Classes (Eq1, Ord1)
 -- >>> :{
 -- data I a = I [a] (Maybe a)
 --   deriving Generic1
@@ -271,7 +277,7 @@
 --
 -- === __Example__
 --
--- >>> :set -XDeriveGeneric -XDerivingVia
+-- >>> import Data.Monoid (Sum(..))
 -- >>> data Point a = Point a a deriving Generic
 -- >>> :{
 --   newtype Vector a = Vector (Point a)
diff --git a/src/Generic/Data/Internal/Meta.hs b/src/Generic/Data/Internal/Meta.hs
--- a/src/Generic/Data/Internal/Meta.hs
+++ b/src/Generic/Data/Internal/Meta.hs
@@ -94,6 +94,7 @@
 
 -- | The fixity of the first constructor.
 --
+-- >>> import GHC.Generics ((:*:)(..))
 -- >>> gconFixity (Just 0)
 -- Prefix
 -- >>> gconFixity ([] :*: id)
diff --git a/test/doctest.hs b/test/doctest.hs
deleted file mode 100644
--- a/test/doctest.hs
+++ /dev/null
@@ -1,7 +0,0 @@
-module Main (main) where
-
-import Test.DocTest (doctest)
-import Build_doctests (flags, pkgs, module_sources)
-
-main :: IO ()
-main = doctest (flags ++ pkgs ++ module_sources)