diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Revision history for byte-order
 
+## 0.1.2.0 -- 2020-01-06
+
+* Add a `Bytes` instance for `Word`.
+
 ## 0.1.1.0 -- YYYY-mm-dd
 
 * Add `PrimUnaligned` instance for `Fixed`.
diff --git a/byte-order.cabal b/byte-order.cabal
--- a/byte-order.cabal
+++ b/byte-order.cabal
@@ -1,6 +1,6 @@
 cabal-version: 2.2
 name: byte-order
-version: 0.1.1.0
+version: 0.1.2.0
 synopsis: Portable big-endian and little-endian conversions
 description:
   This library provides an interface to portably work with byte
diff --git a/src/System/ByteOrder/Class.hs b/src/System/ByteOrder/Class.hs
--- a/src/System/ByteOrder/Class.hs
+++ b/src/System/ByteOrder/Class.hs
@@ -16,9 +16,11 @@
 import Data.Int (Int8,Int16,Int32,Int64)
 import Data.Word (Word8,Word16,Word32,Word64)
 import Data.Word (byteSwap16,byteSwap32,byteSwap64)
-import GHC.ByteOrder (ByteOrder(..),targetByteOrder)
-import GHC.ByteOrder (ByteOrder(BigEndian,LittleEndian))
+import GHC.ByteOrder (ByteOrder(BigEndian,LittleEndian),targetByteOrder)
+import GHC.Word (Word(W#))
 
+import qualified GHC.Exts as Exts
+
 -- | Types that are represented as a fixed-sized word. For these
 -- types, the bytes can be swapped. The instances of this class
 -- use byteswapping primitives and compile-time knowledge of native
@@ -65,6 +67,16 @@
     BigEndian -> byteSwap64
     LittleEndian -> id
 
+instance Bytes Word where
+  {-# inline toBigEndian #-}
+  {-# inline toLittleEndian #-}
+  toBigEndian = case targetByteOrder of
+    BigEndian -> id
+    LittleEndian -> byteSwap
+  toLittleEndian = case targetByteOrder of
+    BigEndian -> byteSwap
+    LittleEndian -> id
+
 instance Bytes Int8 where
   {-# inline toBigEndian #-}
   {-# inline toLittleEndian #-}
@@ -131,3 +143,7 @@
 
 instance FixedOrdering 'BigEndian where
   toFixedEndian = toBigEndian
+
+byteSwap :: Word -> Word
+{-# inline byteSwap #-}
+byteSwap (W# w) = W# (Exts.byteSwap# w)
diff --git a/test/Unit.hs b/test/Unit.hs
--- a/test/Unit.hs
+++ b/test/Unit.hs
@@ -17,6 +17,8 @@
   testB
   putStrLn "C"
   testC
+  putStrLn "D"
+  testD
   putStrLn "Finished"
 
 testA :: IO ()
@@ -58,6 +60,19 @@
   expectByte name marr 5 0xAB
   expectByte name marr 6 0xCD
   expectByte name marr 7 0xEF
+
+testD :: IO ()
+testD = do
+  let payload = 0x01234567 :: Word
+  marr <- newByteArray 20
+  setByteArray marr 0 20 (0x00 :: Word8)
+  writeByteArray marr 0 (Fixed @'LittleEndian payload)
+  let name = "testA"
+  expectByte name marr 0 0x67
+  expectByte name marr 1 0x45
+  expectByte name marr 2 0x23
+  expectByte name marr 3 0x01
+  expectByte name marr 4 0x00
 
 expectByte :: String -> MutableByteArray RealWorld -> Int -> Word8 -> IO ()
 expectByte name marr ix w = do