diff --git a/Annex/DirHashes.hs b/Annex/DirHashes.hs
index 1e1991364a..194b4932c5 100644
--- a/Annex/DirHashes.hs
+++ b/Annex/DirHashes.hs
@@ -65,14 +65,14 @@ hashDirs (HashLevels 1) sz s = addTrailingPathSeparator $ take sz s
 hashDirs _ sz s = addTrailingPathSeparator $ take sz s </> drop sz s
 
 hashDirLower :: HashLevels -> Hasher
-hashDirLower n k = hashDirs n 3 $ take 6 $ show $ md5s $ serializeKey' $ nonChunkKey k
+hashDirLower n k = hashDirs n 3 $ take 6 $ show $ md5 $ serializeKey' $ nonChunkKey k
 
 {- This was originally using Data.Hash.MD5 from MissingH. This new version
 - is faster, but ugly as it has to replicate the 4 Word32's that produced. -}
 hashDirMixed :: HashLevels -> Hasher
 hashDirMixed n k = hashDirs n 2 $ take 4 $ concatMap display_32bits_as_dir $
 	encodeWord32 $ map fromIntegral $ Data.ByteArray.unpack $
-		Utility.Hash.md5s $ serializeKey' $ nonChunkKey k
+		Utility.Hash.md5 $ serializeKey' $ nonChunkKey k
   where
 	encodeWord32 (b1:b2:b3:b4:rest) =
 		(shiftL b4 24 .|. shiftL b3 16 .|. shiftL b2 8 .|. b1)
diff --git a/Annex/Export.hs b/Annex/Export.hs
index 2cc110cb83..47a6a75249 100644
--- a/Annex/Export.hs
+++ b/Annex/Export.hs
@@ -42,7 +42,6 @@ exportKey sha = mk <$> catKey sha
 		, keyMtime = Nothing
 		, keyChunkSize = Nothing
 		, keyChunkNum = Nothing
-		, keySerialization = Nothing
 		}
 
 exportTree :: Remote.RemoteConfig -> Bool
diff --git a/Annex/Locations.hs b/Annex/Locations.hs
index 835f7f9eac..9d6f1fe7d2 100644
--- a/Annex/Locations.hs
+++ b/Annex/Locations.hs
@@ -85,6 +85,7 @@ module Annex.Locations (
 import Data.Char
 import Data.Default
 import qualified Data.ByteString.Char8 as S8
+import qualified Data.ByteString.Lazy as L
 
 import Common
 import Key
@@ -515,7 +516,7 @@ keyFile = fromRawFilePath . keyFile'
 
 keyFile' :: Key -> RawFilePath
 keyFile' k = 
-	let b = serializeKey' k
+	let b = L.toStrict (serializeKey' k)
 	in if any (`S8.elem` b) ['&', '%', ':', '/']
 		then S8.concatMap esc b
 		else b
diff --git a/Annex/VariantFile.hs b/Annex/VariantFile.hs
index 9808293be9..acab1e8281 100644
--- a/Annex/VariantFile.hs
+++ b/Annex/VariantFile.hs
@@ -10,7 +10,7 @@ module Annex.VariantFile where
 import Annex.Common
 import Utility.Hash
 
-import qualified Data.ByteString as S
+import qualified Data.ByteString.Lazy as L
 
 variantMarker :: String
 variantMarker = ".variant-"
@@ -41,5 +41,5 @@ variantFile file key
   where
 	doubleconflict = variantMarker `isInfixOf` file
 
-shortHash :: S.ByteString -> String
-shortHash = take 4 . show . md5s
+shortHash :: L.ByteString -> String
+shortHash = take 4 . show . md5
diff --git a/Backend.hs b/Backend.hs
index 5b7b82e40c..2932253aec 100644
--- a/Backend.hs
+++ b/Backend.hs
@@ -58,10 +58,7 @@ genKey source preferredbackend = do
 		Just k -> Just (makesane k, b)
   where
 	-- keyNames should not contain newline characters.
-	makesane k = k
-		{ keyName = S8.map fixbadchar (keyName k)
-		, keySerialization = Nothing
-		}
+	makesane k = k { keyName = S8.map fixbadchar (keyName k) }
 	fixbadchar c
 		| c == '\n' = '_'
 		| otherwise = c
diff --git a/Backend/Hash.hs b/Backend/Hash.hs
index 6c42af19c3..b8977301b3 100644
--- a/Backend/Hash.hs
+++ b/Backend/Hash.hs
@@ -181,7 +181,6 @@ trivialMigrate' oldkey newbackend afile maxextlen
 	| migratable && hasExt oldvariety = Just $ oldkey
 		{ keyName = keyHash oldkey
 		, keyVariety = newvariety
-		, keySerialization = Nothing
 		}
 	{- Fast migration from hash to hashE backend. -}
 	| migratable && hasExt newvariety = case afile of
@@ -190,7 +189,6 @@ trivialMigrate' oldkey newbackend afile maxextlen
 			{ keyName = keyHash oldkey 
 				<> encodeBS (selectExtension maxextlen file)
 			, keyVariety = newvariety
-			, keySerialization = Nothing
 			}
 	{- Upgrade to fix bad previous migration that created a
 	 - non-extension preserving key, with an extension
@@ -198,7 +196,6 @@ trivialMigrate' oldkey newbackend afile maxextlen
 	| newvariety == oldvariety && not (hasExt oldvariety) &&
 		keyHash oldkey /= keyName oldkey = Just $ oldkey
 			{ keyName = keyHash oldkey
-			, keySerialization = Nothing
 			}
 	| otherwise = Nothing
   where
@@ -291,8 +288,5 @@ testKeyBackend =
 	let b = genBackendE (SHA2Hash (HashSize 256))
 	in b { getKey = (fmap addE) <$$> getKey b } 
   where
-	addE k = k
-		{ keyName = keyName k <> longext
-		, keySerialization = Nothing
-		}
+	addE k = k { keyName = keyName k <> longext }
 	longext = ".this-is-a-test-key"
diff --git a/Command/AddUrl.hs b/Command/AddUrl.hs
index cff1166fdb..be008f63aa 100644
--- a/Command/AddUrl.hs
+++ b/Command/AddUrl.hs
@@ -377,10 +377,7 @@ finishDownloadWith tmp u url file = do
 
 {- Adds the url size to the Key. -}
 addSizeUrlKey :: Url.UrlInfo -> Key -> Key
-addSizeUrlKey urlinfo key = key
-	{ keySize = Url.urlSize urlinfo
-	, keySerialization = Nothing
-	}
+addSizeUrlKey urlinfo key = key { keySize = Url.urlSize urlinfo }
 
 {- Adds worktree file to the repository. -}
 addWorkTree :: UUID -> URLString -> FilePath -> Key -> Maybe FilePath -> Annex ()
diff --git a/Key.hs b/Key.hs
index 00aea87352..593d674ccd 100644
--- a/Key.hs
+++ b/Key.hs
@@ -51,18 +51,14 @@ stubKey = Key
 	, keyMtime = Nothing
 	, keyChunkSize = Nothing
 	, keyChunkNum = Nothing
-	, keySerialization = Nothing
 	}
 
 -- Gets the parent of a chunk key.
 nonChunkKey :: Key -> Key
-nonChunkKey k
-	| keyChunkSize k == Nothing && keyChunkNum k == Nothing = k
-	| otherwise = k
-		{ keyChunkSize = Nothing
-		, keyChunkNum = Nothing
-		, keySerialization = Nothing
-		}
+nonChunkKey k = k
+	{ keyChunkSize = Nothing
+	, keyChunkNum = Nothing
+	}
 
 -- Where a chunk key is offset within its parent.
 chunkKeyOffset :: Key -> Maybe Integer
@@ -98,13 +94,10 @@ buildKey k = byteString (formatKeyVariety (keyVariety k))
 	_ ?: Nothing = mempty
 
 serializeKey :: Key -> String
-serializeKey = decodeBS' . serializeKey'
+serializeKey = decodeBL' . serializeKey'
 
-serializeKey' :: Key -> S.ByteString
-serializeKey' k = case keySerialization k of
-	Nothing -> L.toStrict $
-		toLazyByteStringWith (safeStrategy 128 smallChunkSize) L.empty (buildKey k)
-	Just b -> b
+serializeKey' :: Key -> L.ByteString
+serializeKey' = toLazyByteStringWith (safeStrategy 128 smallChunkSize) L.empty . buildKey
 
 {- This is a strict parser for security reasons; a key
  - can contain only 4 fields, which all consist only of numbers.
@@ -134,7 +127,6 @@ keyParser = do
 			, keyMtime = m
 			, keyChunkSize = cs
 			, keyChunkNum = cn
-			, keySerialization = Nothing
 			}
 		else fail "invalid keyName"
   where
@@ -148,10 +140,7 @@ deserializeKey :: String -> Maybe Key
 deserializeKey = deserializeKey' . encodeBS'
 
 deserializeKey' :: S.ByteString -> Maybe Key
-deserializeKey' b = either
-	(const Nothing)
-	(\k -> Just $ k { keySerialization = Just b })
-	(A.parseOnly keyParser b)
+deserializeKey' b = eitherToMaybe $ A.parseOnly keyParser b
 
 {- This splits any extension out of the keyName, returning the 
  - keyName minus extension, and the extension (including leading dot).
@@ -189,7 +178,6 @@ instance Arbitrary Key where
 		<*> ((abs . fromInteger <$>) <$> arbitrary) -- mtime cannot be negative
 		<*> ((abs <$>) <$> arbitrary) -- chunksize cannot be negative
 		<*> ((succ . abs <$>) <$> arbitrary) -- chunknum cannot be 0 or negative
-		<*> pure Nothing
 
 instance Hashable Key where
 	hashIO32 = hashIO32 . serializeKey'
diff --git a/Remote/Helper/Chunked.hs b/Remote/Helper/Chunked.hs
index 595a4c4d63..f3c69c38dd 100644
--- a/Remote/Helper/Chunked.hs
+++ b/Remote/Helper/Chunked.hs
@@ -68,10 +68,7 @@ chunkKeyStream :: Key -> ChunkSize -> ChunkKeyStream
 chunkKeyStream basek chunksize = ChunkKeyStream $ map mk [1..]
   where
 	mk chunknum = sizedk { keyChunkNum = Just chunknum }
-	sizedk = basek
-		{ keyChunkSize = Just (toInteger chunksize)
-		, keySerialization = Nothing
-		}
+	sizedk = basek { keyChunkSize = Just (toInteger chunksize) }
 
 nextChunkKeyStream :: ChunkKeyStream -> (Key, ChunkKeyStream)
 nextChunkKeyStream (ChunkKeyStream (k:l)) = (k, ChunkKeyStream l)
diff --git a/Types/Key.hs b/Types/Key.hs
index 97d548ff78..df0e042606 100644
--- a/Types/Key.hs
+++ b/Types/Key.hs
@@ -23,7 +23,6 @@ data Key = Key
 	, keyMtime :: Maybe EpochTime
 	, keyChunkSize :: Maybe Integer
 	, keyChunkNum :: Maybe Integer
-	, keySerialization :: Maybe S.ByteString -- ^ cached serialization
 	} deriving (Eq, Ord, Read, Show)
 
 {- A filename may be associated with a Key. -}
diff --git a/Upgrade/V1.hs b/Upgrade/V1.hs
index e58e5818f7..c0dafbb842 100644
--- a/Upgrade/V1.hs
+++ b/Upgrade/V1.hs
@@ -150,7 +150,6 @@ readKey1 v
 		, keyVariety = parseKeyVariety (encodeBS b)
 		, keySize = s
 		, keyMtime = t
-		, keySerialization = Nothing
 		}
   where
 	bits = splitc ':' v
diff --git a/Utility/Hash.hs b/Utility/Hash.hs
index 99923fedc7..23b3f26ec5 100644
--- a/Utility/Hash.hs
+++ b/Utility/Hash.hs
@@ -27,7 +27,6 @@ module Utility.Hash (
 	blake2b_512,
 #endif
 	md5,
-	md5s,
 	prop_hashes_stable,
 	Mac(..),
 	calcMac,
@@ -113,9 +112,6 @@ blake2b_512 = hashlazy
 md5 ::  L.ByteString -> Digest MD5
 md5 = hashlazy
 
-md5s ::  S.ByteString -> Digest MD5
-md5s = hash
-
 {- Check that all the hashes continue to hash the same. -}
 prop_hashes_stable :: Bool
 prop_hashes_stable = all (\(hasher, result) -> hasher foo == result)