diff --git a/containers/src/Data/IntMap/Internal.hs b/containers/src/Data/IntMap/Internal.hs
index e6b68cd24..fe0e5c622 100644
--- a/containers/src/Data/IntMap/Internal.hs
+++ b/containers/src/Data/IntMap/Internal.hs
@@ -263,9 +263,6 @@ module Data.IntMap.Internal (
     , showTree
     , showTreeWith
 
-    -- * Internal types
-    , Nat
-
     -- * Utility
     , link
     , linkKey
@@ -333,9 +330,6 @@ import Text.Read
 import qualified Control.Category as Category
 
 
--- A "Nat" is a natural machine word (an unsigned Int)
-type Nat = Word
-
 {--------------------------------------------------------------------
   Types
 --------------------------------------------------------------------}
diff --git a/containers/src/Data/IntSet/Internal.hs b/containers/src/Data/IntSet/Internal.hs
index 5c01ab5fe..af87654ea 100644
--- a/containers/src/Data/IntSet/Internal.hs
+++ b/containers/src/Data/IntSet/Internal.hs
@@ -241,9 +241,6 @@ import Data.Functor.Identity (Identity(..))
 
 infixl 9 \\{-This comment teaches CPP correct behaviour -}
 
--- A "Nat" is a natural machine word (an unsigned Int)
-type Nat = Word
-
 {--------------------------------------------------------------------
   Operators
 --------------------------------------------------------------------}
@@ -1678,18 +1675,18 @@ bitmapOf x = bitmapOfSuffix (suffixOf x)
   The signatures of methods in question are placed after this comment.
 ----------------------------------------------------------------------}
 
-lowestBitSet :: Nat -> Int
-highestBitSet :: Nat -> Int
-foldlBits :: Int -> (a -> Int -> a) -> a -> Nat -> a
-foldl'Bits :: Int -> (a -> Int -> a) -> a -> Nat -> a
-foldrBits :: Int -> (Int -> a -> a) -> a -> Nat -> a
-foldr'Bits :: Int -> (Int -> a -> a) -> a -> Nat -> a
+lowestBitSet :: Word -> Int
+highestBitSet :: Word -> Int
+foldlBits :: Int -> (a -> Int -> a) -> a -> Word -> a
+foldl'Bits :: Int -> (a -> Int -> a) -> a -> Word -> a
+foldrBits :: Int -> (Int -> a -> a) -> a -> Word -> a
+foldr'Bits :: Int -> (Int -> a -> a) -> a -> Word -> a
 #if MIN_VERSION_base(4,11,0)
-foldMapBits :: Semigroup a => Int -> (Int -> a) -> Nat -> a
+foldMapBits :: Semigroup a => Int -> (Int -> a) -> Word -> a
 #else
-foldMapBits :: Monoid a => Int -> (Int -> a) -> Nat -> a
+foldMapBits :: Monoid a => Int -> (Int -> a) -> Word -> a
 #endif
-takeWhileAntitoneBits :: Int -> (Int -> Bool) -> Nat -> Nat
+takeWhileAntitoneBits :: Int -> (Int -> Bool) -> Word -> Word
 
 {-# INLINE lowestBitSet #-}
 {-# INLINE highestBitSet #-}
@@ -1702,7 +1699,7 @@ takeWhileAntitoneBits :: Int -> (Int -> Bool) -> Nat -> Nat
 
 #if defined(__GLASGOW_HASKELL__)
 
-lowestBitMask :: Nat -> Nat
+lowestBitMask :: Word -> Word
 lowestBitMask x = x .&. negate x
 {-# INLINE lowestBitMask #-}
 
@@ -1710,16 +1707,16 @@ lowestBitSet x = countTrailingZeros x
 
 highestBitSet x = WORD_SIZE_IN_BITS - 1 - countLeadingZeros x
 
--- Reverse the order of bits in the Nat.
-revNat :: Nat -> Nat
+-- Reverse the order of bits in the Word.
+revWord :: Word -> Word
 #if WORD_SIZE_IN_BITS==32
-revNat x1 = case ((x1 `shiftRL` 1) .&. 0x55555555) .|. ((x1 .&. 0x55555555) `shiftLL` 1) of
+revWord x1 = case ((x1 `shiftRL` 1) .&. 0x55555555) .|. ((x1 .&. 0x55555555) `shiftLL` 1) of
               x2 -> case ((x2 `shiftRL` 2) .&. 0x33333333) .|. ((x2 .&. 0x33333333) `shiftLL` 2) of
                  x3 -> case ((x3 `shiftRL` 4) .&. 0x0F0F0F0F) .|. ((x3 .&. 0x0F0F0F0F) `shiftLL` 4) of
                    x4 -> case ((x4 `shiftRL` 8) .&. 0x00FF00FF) .|. ((x4 .&. 0x00FF00FF) `shiftLL` 8) of
                      x5 -> ( x5 `shiftRL` 16             ) .|. ( x5               `shiftLL` 16);
 #else
-revNat x1 = case ((x1 `shiftRL` 1) .&. 0x5555555555555555) .|. ((x1 .&. 0x5555555555555555) `shiftLL` 1) of
+revWord x1 = case ((x1 `shiftRL` 1) .&. 0x5555555555555555) .|. ((x1 .&. 0x5555555555555555) `shiftLL` 1) of
               x2 -> case ((x2 `shiftRL` 2) .&. 0x3333333333333333) .|. ((x2 .&. 0x3333333333333333) `shiftLL` 2) of
                  x3 -> case ((x3 `shiftRL` 4) .&. 0x0F0F0F0F0F0F0F0F) .|. ((x3 .&. 0x0F0F0F0F0F0F0F0F) `shiftLL` 4) of
                    x4 -> case ((x4 `shiftRL` 8) .&. 0x00FF00FF00FF00FF) .|. ((x4 .&. 0x00FF00FF00FF00FF) `shiftLL` 8) of
@@ -1740,14 +1737,14 @@ foldl'Bits prefix f z bitmap = go bitmap z
           where !bitmask = lowestBitMask bm
                 !bi = countTrailingZeros bitmask
 
-foldrBits prefix f z bitmap = go (revNat bitmap) z
+foldrBits prefix f z bitmap = go (revWord bitmap) z
   where go 0 acc = acc
         go bm acc = go (bm `xor` bitmask) ((f $! (prefix+(WORD_SIZE_IN_BITS-1)-bi)) acc)
           where !bitmask = lowestBitMask bm
                 !bi = countTrailingZeros bitmask
 
 
-foldr'Bits prefix f z bitmap = go (revNat bitmap) z
+foldr'Bits prefix f z bitmap = go (revWord bitmap) z
   where go 0 acc = acc
         go bm !acc = go (bm `xor` bitmask) ((f $! (prefix+(WORD_SIZE_IN_BITS-1)-bi)) acc)
           where !bitmask = lowestBitMask bm