diff --git a/Data/Mod.hs b/Data/Mod.hs
--- a/Data/Mod.hs
+++ b/Data/Mod.hs
@@ -7,6 +7,10 @@
 -- <https://en.wikipedia.org/wiki/Modular_arithmetic Modular arithmetic>,
 -- promoting moduli to the type level, with an emphasis on performance.
 -- Originally part of <https://hackage.haskell.org/package/arithmoi arithmoi> package.
+--
+-- This module supports moduli of arbitrary size.
+-- Use "Data.Mod.Word" to achieve better performance,
+-- when your moduli fit into 'Word'.
 
 {-# LANGUAGE BangPatterns     #-}
 {-# LANGUAGE CPP              #-}
@@ -36,25 +40,7 @@
 import GHC.Generics
 import GHC.Integer.GMP.Internals
 import GHC.Natural (Natural(..), powModNatural)
-
-#if MIN_VERSION_base(4,11,0)
-import GHC.TypeNats hiding (Mod)
-#elif MIN_VERSION_base(4,10,0)
-import GHC.TypeNats
-#else
-
-import GHC.TypeLits hiding (natVal, someNatVal)
-import qualified GHC.TypeLits as TL
-
-natVal :: KnownNat n => proxy n -> Natural
-natVal = fromInteger . TL.natVal
-
-someNatVal :: Natural -> SomeNat
-someNatVal n = case TL.someNatVal (toInteger n) of
-  Nothing -> error "someNatVal: impossible negative argument"
-  Just sn -> sn
-
-#endif
+import GHC.TypeNats (Nat, KnownNat, natVal)
 
 -- | This data type represents
 -- <https://en.wikipedia.org/wiki/Modular_arithmetic#Integers_modulo_n integers modulo m>,
diff --git a/Data/Mod/Word.hs b/Data/Mod/Word.hs
new file mode 100644
--- /dev/null
+++ b/Data/Mod/Word.hs
@@ -0,0 +1,359 @@
+-- |
+-- Module:      Data.Mod.Word
+-- Copyright:   (c) 2017-2019 Andrew Lelechenko
+-- Licence:     MIT
+-- Maintainer:  Andrew Lelechenko <andrew.lelechenko@gmail.com>
+--
+-- <https://en.wikipedia.org/wiki/Modular_arithmetic Modular arithmetic>,
+-- promoting moduli to the type level, with an emphasis on performance.
+-- Originally part of <https://hackage.haskell.org/package/arithmoi arithmoi> package.
+--
+-- This module supports only moduli, which fit into 'Word'.
+-- Use (slower) "Data.Mod" to handle arbitrary-sized moduli.
+
+{-# LANGUAGE BangPatterns     #-}
+{-# LANGUAGE CPP              #-}
+{-# LANGUAGE DataKinds        #-}
+{-# LANGUAGE DeriveGeneric    #-}
+{-# LANGUAGE KindSignatures   #-}
+{-# LANGUAGE LambdaCase       #-}
+{-# LANGUAGE MagicHash        #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE UnboxedTuples    #-}
+
+module Data.Mod.Word
+  ( Mod
+  , unMod
+  , invertMod
+  , (^%)
+  ) where
+
+import Prelude as P hiding (even)
+import Control.Exception
+import Control.DeepSeq
+import Data.Bits
+#ifdef MIN_VERSION_semirings
+import Data.Euclidean (GcdDomain(..), Euclidean(..), Field)
+import Data.Ratio
+import Data.Semiring (Semiring(..), Ring(..))
+#endif
+import GHC.Exts
+import GHC.Generics
+import GHC.Integer.GMP.Internals
+import GHC.Natural (Natural(..))
+import GHC.TypeNats (Nat, KnownNat, natVal)
+
+-- | This data type represents
+-- <https://en.wikipedia.org/wiki/Modular_arithmetic#Integers_modulo_n integers modulo m>,
+-- equipped with useful instances.
+--
+-- For example, 3 :: 'Mod' 10 stands for the class of integers
+-- congruent to 3 modulo 10: …−17, −7, 3, 13, 23…
+--
+-- >>> :set -XDataKinds
+-- >>> 3 + 8 :: Mod 10
+-- (1 `modulo` 10) -- because 3 + 8 = 11 ≡ 1 (mod 10)
+--
+-- __Warning:__ division by residue, which is not
+-- <https://en.wikipedia.org/wiki/Coprime_integers coprime>
+-- with the modulo, throws 'DivideByZero'.
+-- Consider using 'invertMod' for non-prime moduli.
+newtype Mod (m :: Nat) = Mod
+  { unMod :: Word
+  -- ^ The canonical representative of the residue class,
+  -- always between 0 and m - 1 inclusively.
+  }
+  deriving (Eq, Ord, Generic)
+
+instance NFData (Mod m)
+
+instance KnownNat m => Show (Mod m) where
+  show m = "(" ++ show (unMod m) ++ " `modulo` " ++ show (natVal m) ++ ")"
+
+instance KnownNat m => Enum (Mod m) where
+  succ x = if x == maxBound then throw Overflow  else coerce (succ @Word) x
+  pred x = if x == minBound then throw Underflow else coerce (pred @Word) x
+
+  toEnum   = fromIntegral
+  fromEnum = fromIntegral . unMod
+
+  enumFrom x       = enumFromTo x maxBound
+  enumFromThen x y = enumFromThenTo x y (if y >= x then maxBound else minBound)
+
+  enumFromTo     = coerce (enumFromTo     @Word)
+  enumFromThenTo = coerce (enumFromThenTo @Word)
+
+instance KnownNat m => Bounded (Mod m) where
+  minBound = Mod 0
+  maxBound = let mx = Mod (fromIntegral (natVal mx) - 1) in mx
+
+#if !MIN_VERSION_base(4,12,0)
+addWordC# :: Word# -> Word# -> (# Word#, Int# #)
+addWordC# x# y# = (# z#, word2Int# c# #)
+  where
+    !(# c#, z# #) = x# `plusWord2#` y#
+#endif
+
+addMod :: Natural -> Word -> Word -> Word
+addMod (NatS# m#) (W# x#) (W# y#) =
+  if isTrue# c# || isTrue# (z# `geWord#` m#) then W# (z# `minusWord#` m#) else W# z#
+  where
+    !(# z#, c# #) = x# `addWordC#` y#
+addMod NatJ#{} _ _ = tooLargeModulo
+
+subMod :: Natural -> Word -> Word -> Word
+subMod (NatS# m#) (W# x#) (W# y#) =
+  if isTrue# (x# `geWord#` y#) then W# z# else W# (z# `plusWord#` m#)
+  where
+    z# = x# `minusWord#` y#
+subMod NatJ#{} _ _ = tooLargeModulo
+
+negateMod :: Natural -> Word -> Word
+negateMod _ (W# 0##) = W# 0##
+negateMod (NatS# m#) (W# x#) = W# (m# `minusWord#` x#)
+negateMod NatJ#{} _ = tooLargeModulo
+
+mulMod :: Natural -> Word -> Word -> Word
+mulMod (NatS# m#) (W# x#) (W# y#) = W# r#
+  where
+    !(# z1#, z2# #) = timesWord2# x# y#
+    !(# _, r# #) = quotRemWord2# z1# z2# m#
+mulMod NatJ#{} _ _ = tooLargeModulo
+
+fromIntegerMod :: Natural -> Integer -> Word
+fromIntegerMod (NatS# 0##) !_ = throw DivideByZero
+fromIntegerMod (NatS# m#) (S# x#) =
+  if isTrue# (x# >=# 0#)
+    then W# (int2Word# x# `remWord#` m#)
+    else negateMod (NatS# m#) (W# (int2Word# (negateInt# x#) `remWord#` m#))
+fromIntegerMod (NatS# m#) (Jp# x#) =
+  W# (x# `remBigNatWord` m#)
+fromIntegerMod (NatS# m#) (Jn# x#) =
+  negateMod (NatS# m#) (W# (x# `remBigNatWord` m#))
+fromIntegerMod NatJ#{} _ = tooLargeModulo
+
+fromNaturalMod :: Natural -> Natural -> Word
+fromNaturalMod (NatS# 0##) !_ = throw DivideByZero
+fromNaturalMod (NatS# m#) (NatS# x#) = W# (x# `remWord#` m#)
+fromNaturalMod (NatS# m#) (NatJ# x#) = W# (x# `remBigNatWord` m#)
+fromNaturalMod NatJ#{} _ = tooLargeModulo
+
+tooLargeModulo :: a
+tooLargeModulo = error "modulo does not fit into a machine word"
+
+instance KnownNat m => Num (Mod m) where
+  mx@(Mod !x) + (Mod !y) = Mod $ addMod (natVal mx) x y
+  {-# INLINE (+) #-}
+  mx@(Mod !x) - (Mod !y) = Mod $ subMod (natVal mx) x y
+  {-# INLINE (-) #-}
+  negate mx@(Mod !x) = Mod $ negateMod (natVal mx) x
+  {-# INLINE negate #-}
+  mx@(Mod !x) * (Mod !y) = Mod $ mulMod (natVal mx) x y
+  {-# INLINE (*) #-}
+  abs = id
+  {-# INLINE abs #-}
+  signum = const x
+    where
+      x = if natVal x > 1 then Mod 1 else Mod 0
+  {-# INLINE signum #-}
+  fromInteger x = mx
+    where
+      mx = Mod $ fromIntegerMod (natVal mx) x
+  {-# INLINE fromInteger #-}
+
+#ifdef MIN_VERSION_semirings
+
+instance KnownNat m => Semiring (Mod m) where
+  plus  = (+)
+  {-# INLINE plus #-}
+  times = (*)
+  {-# INLINE times #-}
+  zero  = Mod 0
+  {-# INLINE zero #-}
+  one   = mx
+    where
+      mx = if natVal mx > 1 then Mod 1 else Mod 0
+  {-# INLINE one #-}
+  fromNatural x = mx
+    where
+      mx = Mod $ fromNaturalMod (natVal mx) x
+  {-# INLINE fromNatural #-}
+
+instance KnownNat m => Ring (Mod m) where
+  negate = P.negate
+  {-# INLINE negate #-}
+
+-- | See the warning about division above.
+instance KnownNat m => Fractional (Mod m) where
+  fromRational r = case denominator r of
+    1   -> num
+    den -> num / fromInteger den
+    where
+      num = fromInteger (numerator r)
+  {-# INLINE fromRational #-}
+  recip mx = case invertMod mx of
+    Nothing -> throw DivideByZero
+    Just y  -> y
+  {-# INLINE recip #-}
+
+-- | See the warning about division above.
+instance KnownNat m => GcdDomain (Mod m) where
+  divide x y = Just (x / y)
+  gcd        = const $ const 1
+  lcm        = const $ const 1
+  coprime    = const $ const True
+
+-- | See the warning about division above.
+instance KnownNat m => Euclidean (Mod m) where
+  degree      = const 0
+  quotRem x y = (x / y, 0)
+  quot        = (/)
+  rem         = const $ const 0
+
+-- | See the warning about division above.
+instance KnownNat m => Field (Mod m)
+
+#endif
+
+-- | If an argument is
+-- <https://en.wikipedia.org/wiki/Coprime_integers coprime>
+-- with the modulo, return its modular inverse.
+-- Otherwise return 'Nothing'.
+--
+-- >>> :set -XDataKinds
+-- >>> invertMod 3 :: Mod 10
+-- Just (7 `modulo` 10) -- because 3 * 7 = 21 ≡ 1 (mod 10)
+-- >>> invertMod 4 :: Mod 10
+-- Nothing -- because 4 and 10 are not coprime
+invertMod :: KnownNat m => Mod m -> Maybe (Mod m)
+invertMod mx@(Mod x) = case natVal mx of
+  NatJ#{}   -> tooLargeModulo
+  NatS# 0## -> Nothing
+  NatS# m#  -> Mod <$> invertModWord x (W# m#)
+
+invertModWord :: Word -> Word -> Maybe Word
+invertModWord x m@(W# m#)
+  -- If both x and k are even, no inverse exists
+  | even x, isTrue# (k# `gtWord#` 0##) = Nothing
+  | otherwise = case invertModWordOdd x m' of
+    Nothing -> Nothing
+    -- goDouble cares only about mod 2^k,
+    -- so overflows and underflows in (1 - x * y) are fine
+    Just y -> Just $ goDouble y (1 - x * y)
+  where
+    k# = ctz# m#
+    m' = m `unsafeShiftR` (I# (word2Int# k#))
+
+    xm' = x * m'
+
+    goDouble :: Word -> Word -> Word
+    goDouble acc r@(W# r#)
+      | isTrue# (tz# `geWord#` k#)
+      = acc
+      | otherwise
+      = goDouble (acc + m' `unsafeShiftL` tz) (r - xm' `unsafeShiftL` tz)
+      where
+        tz# = ctz# r#
+        tz = I# (word2Int# tz#)
+
+-- | Extended binary gcd.
+invertModWordOdd :: Word -> Word -> Maybe Word
+invertModWordOdd 0 !_ = Nothing
+invertModWordOdd !x !m = go00 0 m 1 x
+  where
+    halfMp1 :: Word
+    halfMp1 = half m + 1
+
+    -- Both s and s' may be even
+    go00 :: Word -> Word -> Word -> Word -> Maybe Word
+    go00 !r !s !r' !s'
+      | even s = let (# hr, hs #) = doHalf r s in go00 hr hs r' s'
+      | otherwise = go10 r s r' s'
+
+    -- Here s is odd, s' may be even
+    go10 :: Word -> Word -> Word -> Word -> Maybe Word
+    go10 !r !s !r' !s'
+      | even s' = let (# hr', hs' #) = doHalf r' s' in go10 r s hr' hs'
+      | otherwise = go11 r s r' s'
+
+    -- Here s may be even, s' is odd
+    go01 :: Word -> Word -> Word -> Word -> Maybe Word
+    go01 !r !s !r' !s'
+      | even s = let (# hr, hs #) = doHalf r s in go01 hr hs r' s'
+      | otherwise = go11 r s r' s'
+
+    -- Both s and s' are odd
+    go11 :: Word -> Word -> Word -> Word -> Maybe Word
+    go11 !r !s !r' !s' = case s `compare` s' of
+      EQ -> if s == 1 then Just r else Nothing
+      LT -> let newR' = r' - r + if r' >= r then 0 else m in
+            let newS' = s' - s in
+            let (# hr', hs' #) = doHalf newR' newS' in
+            go10 r s hr' hs'
+      GT -> let newR = r - r' + if r >= r' then 0 else m in
+            let newS = s - s' in
+            let (# hr, hs #) = doHalf newR newS in
+            go01 hr hs r' s'
+
+    doHalf :: Word -> Word -> (# Word, Word #)
+    doHalf r s = (# half r + if even r then 0 else halfMp1, half s #)
+    {-# INLINE doHalf #-}
+
+even :: Word -> Bool
+even x = (x .&. 1) == 0
+{-# INLINE even #-}
+
+half :: Word -> Word
+half x = x `shiftR` 1
+{-# INLINE half #-}
+
+-- | Drop-in replacement for 'Prelude.^' with a bit better performance.
+-- Negative powers are allowed, but may throw 'DivideByZero', if an argument
+-- is not <https://en.wikipedia.org/wiki/Coprime_integers coprime> with the modulo.
+--
+-- Building with @-O@ triggers a rewrite rule 'Prelude.^' = '^%'.
+--
+-- >>> :set -XDataKinds
+-- >>> 3 ^% 4 :: Mod 10
+-- (1 `modulo` 10) -- because 3 ^ 4 = 81 ≡ 1 (mod 10)
+-- >>> 3 ^% (-1) :: Mod 10
+-- (7 `modulo` 10) -- because 3 * 7 = 21 ≡ 1 (mod 10)
+-- >>> 4 ^% (-1) :: Mod 10
+-- (*** Exception: divide by zero -- because 4 and 10 are not coprime
+(^%) :: (KnownNat m, Integral a) => Mod m -> a -> Mod m
+mx@(Mod (W# x#)) ^% a = case natVal mx of
+  NatJ#{} -> tooLargeModulo
+  NatS# m#
+    | a < 0 -> case invertMod mx of
+      Nothing            -> throw DivideByZero
+      Just (Mod (W# y#)) -> Mod $ W# (f y# (- a) 1##)
+    | otherwise          -> Mod $ W# (f x# a 1##)
+    where
+      f :: Integral a => Word# -> a -> Word# -> Word#
+      f _  0 acc# = acc#
+      f b# e acc# = f bb# (e `P.quot` 2) (if odd e then ba# else acc#)
+        where
+          !(# bb1#, bb2# #) = timesWord2# b# b#
+          !(#    _, bb#  #) = quotRemWord2# bb1# bb2# m#
+          !(# ba1#, ba2# #) = timesWord2# b# acc#
+          !(#    _, ba#  #) = quotRemWord2# ba1# ba2# m#
+{-# INLINABLE [1] (^%) #-}
+
+{-# SPECIALISE [1] (^%) ::
+  KnownNat m => Mod m -> Integer -> Mod m,
+  KnownNat m => Mod m -> Natural -> Mod m,
+  KnownNat m => Mod m -> Int     -> Mod m,
+  KnownNat m => Mod m -> Word    -> Mod m #-}
+
+{-# RULES
+"powMod"               forall (x :: KnownNat m => Mod m) p. x ^ p = x ^% p
+
+"powMod/2/Integer"     forall x. x ^% (2 :: Integer) = let u = x in u*u
+"powMod/3/Integer"     forall x. x ^% (3 :: Integer) = let u = x in u*u*u
+"powMod/2/Int"         forall x. x ^% (2 :: Int)     = let u = x in u*u
+"powMod/3/Int"         forall x. x ^% (3 :: Int)     = let u = x in u*u*u
+"powMod/2/Word"        forall x. x ^% (2 :: Word)    = let u = x in u*u
+"powMod/3/Word"        forall x. x ^% (3 :: Word)    = let u = x in u*u*u
+#-}
+
+infixr 8 ^%
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -66,6 +66,15 @@
   Even less expected is that `50 :: Mod Word8 300` appears to be `6`
   (remember that type-level numbers are always `Natural`).
 
+## Citius, altius, fortius!
+
+If you are looking for an ultimate performance
+and your moduli fit into `Word`,
+try `Data.Mod.Word`,
+which is a drop-in replacement of `Data.Mod`,
+but offers 3x faster addition,
+2x faster multiplication and much less allocations.
+
 ## What's next?
 
 This package was cut out of [`arithmoi`](https://hackage.haskell.org/package/arithmoi)
diff --git a/bench/Bench.hs b/bench/Bench.hs
new file mode 100644
--- /dev/null
+++ b/bench/Bench.hs
@@ -0,0 +1,116 @@
+{-# LANGUAGE DataKinds #-}
+
+{-# OPTIONS_GHC -fno-warn-type-defaults -fno-warn-name-shadowing #-}
+
+module Main where
+
+import Data.Maybe
+import Data.Time.Clock
+import System.IO
+
+import qualified Data.Mod
+import qualified Data.Mod.Word
+-- import qualified Data.Modular
+-- import qualified Numeric.Modular
+
+benchAddition :: IO ()
+benchAddition = do
+  putStrLn "Addition"
+
+  t0 <- getCurrentTime
+  print (sum [1..10^7] :: Data.Mod.Word.Mod 1000000007)
+  t1 <- getCurrentTime
+  putStrLn $ "Data.Mod.Word   " ++ show (diffUTCTime t1 t0)
+
+  t0 <- getCurrentTime
+  print (sum [1..10^7] :: Data.Mod.Mod 1000000007)
+  t1 <- getCurrentTime
+  putStrLn $ "Data.Mod        " ++ show (diffUTCTime t1 t0)
+
+  -- t0 <- getCurrentTime
+  -- print (sum [1..10^7] :: Data.Modular.Mod Integer 1000000007)
+  -- t1 <- getCurrentTime
+  -- putStrLn $ "Data.Modular    " ++ show (diffUTCTime t1 t0)
+
+  -- t0 <- getCurrentTime
+  -- print (sum (map fromIntegral [1..10^7]) :: Numeric.Modular.Mod 1000000007)
+  -- t1 <- getCurrentTime
+  -- putStrLn $ "Numeric.Modular " ++ show (diffUTCTime t1 t0)
+
+benchProduct :: IO ()
+benchProduct = do
+  putStrLn "Product"
+
+  t0 <- getCurrentTime
+  print (product [1..10^7] :: Data.Mod.Word.Mod 1000000007)
+  t1 <- getCurrentTime
+  putStrLn $ "Data.Mod.Word   " ++ show (diffUTCTime t1 t0)
+
+  t0 <- getCurrentTime
+  print (product [1..10^7] :: Data.Mod.Mod 1000000007)
+  t1 <- getCurrentTime
+  putStrLn $ "Data.Mod        " ++ show (diffUTCTime t1 t0)
+
+  -- t0 <- getCurrentTime
+  -- print (product [1..10^7] :: Data.Modular.Mod Integer 1000000007)
+  -- t1 <- getCurrentTime
+  -- putStrLn $ "Data.Modular    " ++ show (diffUTCTime t1 t0)
+
+  -- t0 <- getCurrentTime
+  -- print (product (map fromIntegral [1..10^7]) :: Numeric.Modular.Mod 1000000007)
+  -- t1 <- getCurrentTime
+  -- putStrLn $ "Numeric.Modular " ++ show (diffUTCTime t1 t0)
+
+benchInversion :: IO ()
+benchInversion = do
+  putStrLn "Inversion"
+
+  t0 <- getCurrentTime
+  print (sum (map (fromJust . Data.Mod.Word.invertMod) [1 ..10^6]) :: Data.Mod.Word.Mod 1000000007)
+  t1 <- getCurrentTime
+  putStrLn $ "Data.Mod.Word   " ++ show (diffUTCTime t1 t0)
+
+  t0 <- getCurrentTime
+  print (sum (map (fromJust . Data.Mod.invertMod) [1 ..10^6]) :: Data.Mod.Mod 1000000007)
+  t1 <- getCurrentTime
+  putStrLn $ "Data.Mod        " ++ show (diffUTCTime t1 t0)
+
+  -- t0 <- getCurrentTime
+  -- print (sum (map Data.Modular.inv [1..10^6]) :: Data.Modular.Mod Integer 1000000007)
+  -- t1 <- getCurrentTime
+  -- putStrLn $ "Data.Modular    " ++ show (diffUTCTime t1 t0)
+
+benchPower :: IO ()
+benchPower = do
+  putStrLn "Power"
+
+  t0 <- getCurrentTime
+  print (sum (map (2 ^) [1..10^6]) :: Data.Mod.Word.Mod 1000000007)
+  t1 <- getCurrentTime
+  putStrLn $ "Data.Mod.Word   " ++ show (diffUTCTime t1 t0)
+
+  t0 <- getCurrentTime
+  print (sum (map (2 ^) [1..10^6]) :: Data.Mod.Mod 1000000007)
+  t1 <- getCurrentTime
+  putStrLn $ "Data.Mod        " ++ show (diffUTCTime t1 t0)
+
+  -- t0 <- getCurrentTime
+  -- print (sum (map (2 ^) [1..10^6]) :: Data.Modular.Mod Integer 1000000007)
+  -- t1 <- getCurrentTime
+  -- putStrLn $ "Data.Modular    " ++ show (diffUTCTime t1 t0)
+
+  -- t0 <- getCurrentTime
+  -- print (sum (map (2 ^) [1..10^6]) :: Numeric.Modular.Mod 1000000007)
+  -- t1 <- getCurrentTime
+  -- putStrLn $ "Numeric.Modular " ++ show (diffUTCTime t1 t0)
+
+main :: IO ()
+main = do
+  hSetBuffering stdout LineBuffering
+  benchAddition
+  putStrLn ""
+  benchProduct
+  putStrLn ""
+  benchInversion
+  putStrLn ""
+  benchPower
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,7 @@
+# 0.1.1.0
+
+* Add `Data.Mod.Word`.
+
 # 0.1.0.0
 
 * Initial release
diff --git a/mod.cabal b/mod.cabal
--- a/mod.cabal
+++ b/mod.cabal
@@ -1,5 +1,5 @@
 name:          mod
-version:       0.1.0.0
+version:       0.1.1.0
 cabal-version: >=1.10
 build-type:    Simple
 license:       MIT
@@ -15,7 +15,7 @@
   Originally part of <https://hackage.haskell.org/package/arithmoi arithmoi> package.
 category:      Math, Number Theory
 author:        Andrew Lelechenko <andrew.lelechenko@gmail.com>
-tested-with:   GHC ==8.0.2 GHC ==8.2.2 GHC ==8.4.4 GHC ==8.6.5 GHC ==8.8.1
+tested-with:   GHC ==8.2.2 GHC ==8.4.4 GHC ==8.6.5 GHC ==8.8.1
 extra-source-files:
   changelog.md
   README.md
@@ -30,7 +30,7 @@
 
 library
   build-depends:
-    base >=4.9 && <5,
+    base >=4.10 && <5,
     deepseq,
     integer-gmp <1.1
   if flag(semirings)
@@ -38,12 +38,13 @@
       semirings >= 0.5
   exposed-modules:
     Data.Mod
+    Data.Mod.Word
   default-language: Haskell2010
   ghc-options: -Wall
 
 test-suite mod-tests
   build-depends:
-    base >=4.9 && <5,
+    base >=4.10 && <5,
     mod,
     quickcheck-classes-base,
     tasty >=0.10,
@@ -56,4 +57,17 @@
   main-is: Test.hs
   default-language: Haskell2010
   hs-source-dirs: test
+  ghc-options: -Wall
+
+benchmark mod-bench
+  build-depends:
+    base,
+    mod,
+    -- modular,
+    -- modular-arithmetic,
+    time
+  type: exitcode-stdio-1.0
+  main-is: Bench.hs
+  default-language: Haskell2010
+  hs-source-dirs: bench
   ghc-options: -Wall
diff --git a/test/Test.hs b/test/Test.hs
--- a/test/Test.hs
+++ b/test/Test.hs
@@ -1,12 +1,17 @@
-{-# LANGUAGE CPP       #-}
-{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE CPP                 #-}
+{-# LANGUAGE DataKinds           #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications    #-}
 
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 module Main where
 
 import Data.Mod
+import qualified Data.Mod.Word as Word
 import Data.Proxy
+import Data.Semigroup
+import GHC.TypeNats (KnownNat, SomeNat(..), natVal, someNatVal)
 import Test.Tasty
 import Test.Tasty.QuickCheck
 import Test.QuickCheck.Classes.Base
@@ -16,24 +21,64 @@
 import Test.QuickCheck.Classes
 #endif
 
-#if MIN_VERSION_base(4,11,0)
-import GHC.TypeNats hiding (Mod)
-#elif MIN_VERSION_base(4,10,0)
-import GHC.TypeNats
-#else
-import GHC.TypeLits
-#endif
-
 main :: IO ()
 main = defaultMain $ testGroup "All"
   [ testGroup "Mod 1" $
-    map lawsToTest $ laws1 (Proxy :: Proxy (Mod 1))
+    testProperty "fromInteger"
+      (fromIntegerProp (Proxy :: Proxy 1)) :
+    map lawsToTest (laws1 (Proxy :: Proxy (Mod 1)))
   , testGroup "Mod 2310" $
-    map lawsToTest $ laws (Proxy :: Proxy (Mod 2310))
+    testProperty "fromInteger"
+      (fromIntegerProp (Proxy :: Proxy 2310)) :
+    testProperty "invertMod"   (invertModProp   @2310) :
+    testProperty "powMod"      (powModProp      @2310) :
+    map lawsToTest (laws (Proxy :: Proxy (Mod 2310)))
+  , testGroup "Mod 18446744073709551615" $
+    testProperty "fromInteger"
+      (fromIntegerProp (Proxy :: Proxy 18446744073709551615)) :
+    testProperty "invertMod"   (invertModProp   @18446744073709551615) :
+    testProperty "powMod"      (powModProp      @18446744073709551615) :
+    map lawsToTest (laws (Proxy :: Proxy (Mod 18446744073709551615)))
   , testGroup "Mod 18446744073709551626" $
-    map lawsToTest $ laws (Proxy :: Proxy (Mod 18446744073709551626))
+    testProperty "fromInteger"
+      (fromIntegerProp (Proxy :: Proxy 18446744073709551626)) :
+    testProperty "powMod"      (powModProp      @18446744073709551626) :
+    testProperty "invertMod"   (invertModProp   @18446744073709551626) :
+    map lawsToTest (laws (Proxy :: Proxy (Mod 18446744073709551626)))
   , testGroup "Mod 123456789012345678901234567890" $
-    map lawsToTest $ laws (Proxy :: Proxy (Mod 123456789012345678901234567890))
+    testProperty "fromInteger"
+      (fromIntegerProp (Proxy :: Proxy 123456789012345678901234567890)) :
+    testProperty "powMod"      (powModProp      @123456789012345678901234567890) :
+    testProperty "invertMod"   (invertModProp   @123456789012345678901234567890) :
+    map lawsToTest (laws (Proxy :: Proxy (Mod 123456789012345678901234567890)))
+  , testGroup "Random Mod" $
+    [ testProperty "fromInteger" fromIntegerRandomProp
+    , testProperty "invertMod"   invertModRandomProp
+    , testProperty "powMod"      powModRandomProp
+    ]
+
+  , testGroup "Word.Mod 1" $
+    testProperty "fromInteger"
+      (fromIntegerWordProp (Proxy :: Proxy 1)) :
+    map lawsToTest (laws1 (Proxy :: Proxy (Word.Mod 1)))
+  , testGroup "Word.Mod 2310" $
+    testProperty "fromInteger"
+      (fromIntegerWordProp (Proxy :: Proxy 2310)) :
+    testProperty "powMod"    (powModWordProp    @2310) :
+    testProperty "invertMod" (invertModWordProp @2310) :
+    map lawsToTest (laws (Proxy :: Proxy (Word.Mod 2310)))
+  , testGroup "Word.Mod 18446744073709551615" $
+    testProperty "fromInteger"
+      (fromIntegerWordProp (Proxy :: Proxy 18446744073709551615)) :
+    testProperty "powMod"    (powModWordProp    @18446744073709551615) :
+    testProperty "invertMod" (invertModWordProp @18446744073709551615) :
+    map lawsToTest (laws (Proxy :: Proxy (Word.Mod 18446744073709551615)))
+  , testGroup "Random Word.Mod" $
+    [ testProperty "fromInteger" fromIntegerWordRandomProp
+    , testProperty "invertMod"   invertModWordRandomProp
+    , testProperty "invertMod near maxBound" invertModWordRandomProp_nearMaxBound
+    , testProperty "powMod"      powModWordRandomProp
+    ]
   ]
 
 #ifdef MIN_VERSION_semirings
@@ -65,3 +110,86 @@
 
 instance KnownNat m => Arbitrary (Mod m) where
   arbitrary = oneof [arbitraryBoundedEnum, fromInteger <$> arbitrary]
+  shrink = map fromInteger . shrink . toInteger . unMod
+
+instance KnownNat m => Arbitrary (Word.Mod m) where
+  arbitrary = oneof [arbitraryBoundedEnum, fromInteger <$> arbitrary]
+  shrink = map fromIntegral . shrink . Word.unMod
+
+-------------------------------------------------------------------------------
+-- fromInteger
+
+fromIntegerRandomProp :: Positive Integer -> Integer -> Property
+fromIntegerRandomProp (Positive m) n = m > 1 ==> case someNatVal (fromInteger m) of
+  SomeNat p -> fromIntegerProp p n
+
+fromIntegerProp :: forall m. KnownNat m => Proxy m -> Integer -> Property
+fromIntegerProp p n = unMod m === fromInteger (n `mod` toInteger (natVal p))
+  where
+    m :: Mod m
+    m = fromInteger n
+
+fromIntegerWordRandomProp :: Word -> Integer -> Property
+fromIntegerWordRandomProp m n = m > 1 ==> case someNatVal (fromIntegral m) of
+  SomeNat p -> fromIntegerWordProp p n
+
+fromIntegerWordProp :: forall m. KnownNat m => Proxy m -> Integer -> Property
+fromIntegerWordProp p n = Word.unMod m === fromInteger (n `mod` toInteger (natVal p))
+  where
+    m :: Word.Mod m
+    m = fromInteger n
+
+-------------------------------------------------------------------------------
+-- invertMod
+
+invertModRandomProp :: Positive Integer -> Integer -> Property
+invertModRandomProp (Positive m) n = m > 1 ==> case someNatVal (fromInteger m) of
+  SomeNat (Proxy :: Proxy m) -> invertModProp (fromInteger n :: Mod m)
+
+invertModProp :: KnownNat m => Mod m -> Property
+invertModProp x = case invertMod x of
+  Nothing -> g =/= 1
+  Just x' -> g === 1 .&&. x * x' === 1 .&&. x' * x === 1 .&&. x' === x ^% (-1 :: Int)
+  where
+    g = gcd (unMod x) (fromIntegral (natVal x))
+
+invertModWordRandomProp :: Word -> Integer -> Property
+invertModWordRandomProp m n = m > 1 ==> case someNatVal (fromIntegral m) of
+  SomeNat (Proxy :: Proxy m) -> invertModWordProp (fromInteger n :: Word.Mod m)
+
+invertModWordRandomProp_nearMaxBound :: Word -> Integer -> Property
+invertModWordRandomProp_nearMaxBound m n = m < maxBound ==>
+  case someNatVal (fromIntegral (maxBound - m)) of
+    SomeNat (Proxy :: Proxy m) -> invertModWordProp (fromInteger n :: Word.Mod m)
+
+invertModWordProp :: KnownNat m => Word.Mod m -> Property
+invertModWordProp x = case Word.invertMod x of
+  Nothing -> g =/= 1
+  Just x' -> g === 1 .&&. x * x' === 1 .&&. x' * x === 1 .&&. x' === x Word.^% (-1 :: Int)
+  where
+    g = gcd (Word.unMod x) (fromIntegral (natVal x))
+
+-------------------------------------------------------------------------------
+-- powMod
+
+powModRandomProp :: Positive Integer -> Integer -> Int -> Property
+powModRandomProp (Positive m) n k = m > 1 ==> case someNatVal (fromInteger m) of
+  SomeNat (Proxy :: Proxy m) -> powModProp (fromInteger n :: Mod m) k
+
+powModProp :: KnownNat m => Mod m -> Int -> Property
+powModProp x n
+  | n >= 0 = x ^% n === getProduct (stimes n (Product x))
+  | otherwise = case invertMod x of
+    Nothing -> property True
+    Just x' -> x ^% n === getProduct (stimes (-n) (Product x'))
+
+powModWordRandomProp :: Word -> Integer -> Int -> Property
+powModWordRandomProp m n k = m > 1 ==> case someNatVal (fromIntegral m) of
+  SomeNat (Proxy :: Proxy m) -> powModWordProp (fromInteger n :: Word.Mod m) k
+
+powModWordProp :: KnownNat m => Word.Mod m -> Int -> Property
+powModWordProp x n
+  | n >= 0 = x Word.^% n === getProduct (stimes n (Product x))
+  | otherwise = case Word.invertMod x of
+    Nothing -> property True
+    Just x' -> x Word.^% n === getProduct (stimes (-n) (Product x'))
