diff --git a/app/App/Codec.hs b/app/App/Codec.hs
--- a/app/App/Codec.hs
+++ b/app/App/Codec.hs
@@ -2,7 +2,6 @@
   ( decodeWord32s
   ) where
 
-import Data.Semigroup ((<>))
 import Data.Word
 
 import qualified Data.Binary.Get      as G
diff --git a/app/App/Commands.hs b/app/App/Commands.hs
--- a/app/App/Commands.hs
+++ b/app/App/Commands.hs
@@ -2,7 +2,6 @@
 
 import App.Commands.CreateIndex
 import App.Commands.LoadSave
-import Data.Semigroup           ((<>))
 import Options.Applicative
 
 commands :: Parser (IO ())
diff --git a/app/App/Commands/CreateIndex.hs b/app/App/Commands/CreateIndex.hs
--- a/app/App/Commands/CreateIndex.hs
+++ b/app/App/Commands/CreateIndex.hs
@@ -11,7 +11,6 @@
 import Control.Monad.IO.Class
 import Control.Monad.Trans.Resource
 import Data.Generics.Product.Any
-import Data.Semigroup                          ((<>))
 import Data.Word
 import HaskellWorks.Data.Bits.BitWise
 import HaskellWorks.Data.Bits.Log2
diff --git a/app/App/Commands/LoadSave.hs b/app/App/Commands/LoadSave.hs
--- a/app/App/Commands/LoadSave.hs
+++ b/app/App/Commands/LoadSave.hs
@@ -9,7 +9,6 @@
 import App.Codec
 import Control.Lens
 import Data.Generics.Product.Any
-import Data.Semigroup                       ((<>))
 import Data.Word
 import HaskellWorks.Data.RankSelect.CsPoppy
 import Options.Applicative                  hiding (columns)
diff --git a/app/Main.hs b/app/Main.hs
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -2,7 +2,6 @@
 
 import App.Commands
 import Control.Monad
-import Data.Semigroup      ((<>))
 import Options.Applicative
 
 main :: IO ()
diff --git a/bench/Main.hs b/bench/Main.hs
--- a/bench/Main.hs
+++ b/bench/Main.hs
@@ -4,7 +4,6 @@
 module Main where
 
 import Criterion.Main
-import Data.Monoid                         ((<>))
 import Foreign                             hiding ((.&.))
 import HaskellWorks.Data.Bits.BitWise
 import HaskellWorks.Data.EliasFano
diff --git a/doctest/DoctestDriver.hs b/doctest/DoctestDriver.hs
new file mode 100644
--- /dev/null
+++ b/doctest/DoctestDriver.hs
@@ -0,0 +1,12 @@
+{-# LANGUAGE CPP #-}
+
+#if MIN_VERSION_GLASGOW_HASKELL(8,4,4,0)
+{-# OPTIONS_GHC -F -pgmF doctest-discover #-}
+#else
+module Main where
+
+import qualified System.IO as IO
+
+main :: IO ()
+main = IO.putStrLn "WARNING: doctest will not run on GHC versions earlier than 8.4.4"
+#endif
diff --git a/hw-eliasfano.cabal b/hw-eliasfano.cabal
--- a/hw-eliasfano.cabal
+++ b/hw-eliasfano.cabal
@@ -1,7 +1,7 @@
-cabal-version:  2.2
+cabal-version: 2.2
 
 name:                   hw-eliasfano
-version:                0.1.1.1
+version:                0.1.2.0
 synopsis:               Elias-Fano
 description:            Please see README.md
 category:               Data, Succinct Data Structures, Data Structures
@@ -9,10 +9,10 @@
 bug-reports:            https://github.com/haskell-works/hw-eliasfano/issues
 author:                 John Ky
 maintainer:             newhoggy@gmail.com
-copyright:              2016-2019 John Ky
+copyright:              2016-2020 John Ky
 license:                BSD-3-Clause
 license-file:           LICENSE
-tested-with:            GHC == 8.8.1, GHC == 8.6.5, GHC == 8.4.4, GHC == 8.2.2
+tested-with:            GHC == 8.10.1, GHC == 8.8.3, GHC == 8.6.5, GHC == 8.4.4
 build-type:             Simple
 extra-source-files:     README.md
 
@@ -20,36 +20,39 @@
   type: git
   location: https://github.com/haskell-works/hw-eliasfano
 
-common base                 { build-depends: base                 >= 4          &&  < 5     }
-
-common bytestring           { build-depends: bytestring           >= 0.10.8.2   && < 0.11   }
-common binary               { build-depends: binary               >= 0.8        && < 0.9    }
-common criterion            { build-depends: criterion            >= 1.5.5.0    && < 1.6    }
-common deepseq              { build-depends: deepseq              >= 1.4        && < 1.5    }
-common generic-lens         { build-depends: generic-lens         >= 1.2.0.1    && < 1.3    }
-common hedgehog             { build-depends: hedgehog             >= 0.6        && < 1.1    }
-common hspec                { build-depends: hspec                >= 2.7.1      && < 3      }
-common hw-bits              { build-depends: hw-bits              >= 0.7.0.6    && < 0.8    }
-common hw-hedgehog          { build-depends: hw-hedgehog          >= 0.1.0.3    && < 0.2    }
-common hw-hspec-hedgehog    { build-depends: hw-hspec-hedgehog    >= 0.1.0.7    && < 0.2    }
-common hw-int               { build-depends: hw-int               >= 0.0.0.3    && < 0.1    }
-common hw-packed-vector     { build-depends: hw-packed-vector     >= 0.0.0.3    && < 0.1    }
-common hw-prim              { build-depends: hw-prim              >= 0.6.2.26   && < 0.7    }
-common hw-rankselect        { build-depends: hw-rankselect        >= 0.13       && < 0.14   }
-common hw-rankselect-base   { build-depends: hw-rankselect-base   >= 0.3.2.1    && < 0.4    }
-common lens                 { build-depends: lens                 >= 4          && < 5      }
-common mmap                 { build-depends: mmap                 >= 0.5.9      && < 0.6    }
-common optparse-applicative { build-depends: optparse-applicative >= 0.14       && < 0.16   }
-common resourcet            { build-depends: resourcet            >= 1.2.2      && < 1.3    }
-common temporary-resourcet  { build-depends: temporary-resourcet  >= 0.1.0.1    && < 0.2    }
-common vector               { build-depends: vector               >= 0.12.0.3   && < 0.13   }
+common base                       { build-depends: base                       >= 4.11       && < 5      }
 
-common semigroups   { if impl(ghc <  8    ) { build-depends: semigroups     >= 0.16     && < 0.19 } }
+common bytestring                 { build-depends: bytestring                 >= 0.10.8.2   && < 0.11   }
+common binary                     { build-depends: binary                     >= 0.8        && < 0.9    }
+common criterion                  { build-depends: criterion                  >= 1.5.5.0    && < 1.6    }
+common deepseq                    { build-depends: deepseq                    >= 1.4        && < 1.5    }
+common doctest                    { build-depends: doctest                    >= 0.16.2     && < 0.17   }
+common doctest-discover           { build-depends: doctest-discover           >= 0.2        && < 0.3    }
+common generic-lens               { build-depends: generic-lens               >= 1.2.0.1    && < 1.3    }
+common hedgehog                   { build-depends: hedgehog                   >= 0.6        && < 1.1    }
+common hspec                      { build-depends: hspec                      >= 2.7.1      && < 3      }
+common hw-bits                    { build-depends: hw-bits                    >= 0.7.0.6    && < 0.8    }
+common hw-hedgehog                { build-depends: hw-hedgehog                >= 0.1.0.3    && < 0.2    }
+common hw-hspec-hedgehog          { build-depends: hw-hspec-hedgehog          >= 0.1.0.7    && < 0.2    }
+common hw-int                     { build-depends: hw-int                     >= 0.0.0.3    && < 0.1    }
+common hw-packed-vector           { build-depends: hw-packed-vector           >= 0.2.0.1    && < 0.3    }
+common hw-prim                    { build-depends: hw-prim                    >= 0.6.2.26   && < 0.7    }
+common hw-rankselect              { build-depends: hw-rankselect              >= 0.13       && < 0.14   }
+common hw-rankselect-base         { build-depends: hw-rankselect-base         >= 0.3.2.1    && < 0.4    }
+common lens                       { build-depends: lens                       >= 4          && < 5      }
+common mmap                       { build-depends: mmap                       >= 0.5.9      && < 0.6    }
+common optparse-applicative       { build-depends: optparse-applicative       >= 0.14       && < 0.16   }
+common resourcet                  { build-depends: resourcet                  >= 1.2.2      && < 1.3    }
+common temporary-resourcet        { build-depends: temporary-resourcet        >= 0.1.0.1    && < 0.2    }
+common vector                     { build-depends: vector                     >= 0.12.0.3   && < 0.13   }
 
 common config
   default-language:     Haskell2010
   ghc-options:          -Wall
 
+common hw-eliasfano
+  build-depends:        hw-eliasfano
+
 library
   import:               base, config
                       , deepseq
@@ -73,6 +76,7 @@
                       , bytestring
                       , generic-lens
                       , hw-bits
+                      , hw-eliasfano
                       , hw-packed-vector
                       , hw-prim
                       , hw-rankselect
@@ -80,13 +84,11 @@
                       , lens
                       , optparse-applicative
                       , resourcet
-                      , semigroups
                       , temporary-resourcet
                       , vector
   main-is:              Main.hs
   hs-source-dirs:       app
   ghc-options:          -threaded -rtsopts -with-rtsopts=-N -O2
-  build-depends:        hw-eliasfano
   other-modules:        App.Codec
                         App.Commands
                         App.Commands.CreateIndex
@@ -98,6 +100,7 @@
                       , hedgehog
                       , hspec
                       , hw-bits
+                      , hw-eliasfano
                       , hw-hedgehog
                       , hw-hspec-hedgehog
                       , hw-int
@@ -109,13 +112,10 @@
   type:                 exitcode-stdio-1.0
   main-is:              Spec.hs
   hs-source-dirs:       test
-  ghc-options:          -Wall -threaded -rtsopts -with-rtsopts=-N
-  build-depends:        hw-eliasfano
+  ghc-options:          -threaded -rtsopts -with-rtsopts=-N
   other-modules:        HaskellWorks.Data.EliasFano.Reference
                         HaskellWorks.Data.EliasFano.ReferenceSpec
                         HaskellWorks.Data.EliasFanoSpec
-                        Paths_hw_eliasfano
-  autogen-modules:      Paths_hw_eliasfano
   default-language:     Haskell2010
   build-tool-depends:   hspec-discover:hspec-discover
 
@@ -127,6 +127,7 @@
                       , hedgehog
                       , hspec
                       , hw-bits
+                      , hw-eliasfano
                       , hw-hedgehog
                       , hw-hspec-hedgehog
                       , hw-int
@@ -137,6 +138,15 @@
   type:                 exitcode-stdio-1.0
   main-is:              Main.hs
   hs-source-dirs:       bench
-  other-modules:        Paths_hw_eliasfano
-  build-depends:        hw-eliasfano
-  autogen-modules:      Paths_hw_eliasfano
+
+test-suite doctest
+  import:               base, config
+                      , doctest
+                      , doctest-discover
+                      , hw-eliasfano
+  default-language:     Haskell2010
+  type:                 exitcode-stdio-1.0
+  ghc-options:          -threaded
+  main-is:              DoctestDriver.hs
+  HS-Source-Dirs:       doctest
+  build-tool-depends:   doctest-discover:doctest-discover
diff --git a/test/HaskellWorks/Data/EliasFano/ReferenceSpec.hs b/test/HaskellWorks/Data/EliasFano/ReferenceSpec.hs
--- a/test/HaskellWorks/Data/EliasFano/ReferenceSpec.hs
+++ b/test/HaskellWorks/Data/EliasFano/ReferenceSpec.hs
@@ -11,7 +11,7 @@
 import qualified Hedgehog.Gen   as G
 import qualified Hedgehog.Range as R
 
-{-# ANN module ("HLint: Ignore Redundant do" :: String) #-}
+{-# ANN module ("HLint: ignore Redundant do" :: String) #-}
 
 spec :: Spec
 spec = describe "HaskellWorks.Data.EliasFano.ReferenceSpec" $ do
diff --git a/test/HaskellWorks/Data/EliasFanoSpec.hs b/test/HaskellWorks/Data/EliasFanoSpec.hs
--- a/test/HaskellWorks/Data/EliasFanoSpec.hs
+++ b/test/HaskellWorks/Data/EliasFanoSpec.hs
@@ -17,7 +17,7 @@
 import qualified Hedgehog.Gen                                  as G
 import qualified Hedgehog.Range                                as R
 
-{-# ANN module ("HLint: Ignore Redundant do" :: String) #-}
+{-# ANN module ("HLint: ignore Redundant do" :: String) #-}
 
 spec :: Spec
 spec = describe "HaskellWorks.Data.EliasFanoSpec" $ do
