diff --git a/Backend/SHA.hs b/Backend/SHA.hs
index ef0e92d209..1a278068eb 100644
--- a/Backend/SHA.hs
+++ b/Backend/SHA.hs
@@ -34,6 +34,7 @@ genBackend size = Just $ Backend
 	{ name = shaName size
 	, getKey = keyValue size
 	, fsckKey = Just $ checkKeyChecksum size
+	, canUpgradeKey = Just $ needsUpgrade
 	}
 
 genBackendE :: SHASize -> Maybe Backend
@@ -61,6 +62,8 @@ shaN shasize file filesize = do
 	parse command [] = bad command
 	parse command (l:_)
 		| null sha = bad command
+		-- sha is prefixed with \ when filename contains certian chars
+		| "\\" `isPrefixOf` sha = drop 1 sha
 		| otherwise = sha
 	  where
 		sha = fst $ separate (== ' ') l
@@ -137,6 +140,17 @@ checkKeyChecksum size key file = do
 			check <$> shaN size file filesize
 		_ -> return True
   where
+	sha = keySha key
 	check s
-		| s == dropExtensions (keyName key) = True
+		| s == sha = True
+		{- A bug caused checksums to be prefixed with \ in some
+		 - cases; still accept these as legal now that the bug has been
+		 - fixed. -}
+		| '\\' : s == sha = True
 		| otherwise = False
+
+keySha :: Key -> String
+keySha key = dropExtensions (keyName key)
+
+needsUpgrade :: Key -> Bool
+needsUpgrade key = "\\" `isPrefixOf` keySha key
diff --git a/Backend/URL.hs b/Backend/URL.hs
index 81c287cfd4..9e1652970a 100644
--- a/Backend/URL.hs
+++ b/Backend/URL.hs
@@ -24,6 +24,7 @@ backend = Backend
 	{ name = "URL"
 	, getKey = const $ return Nothing
 	, fsckKey = Nothing
+	, canUpgradeKey = Nothing
 	}
 
 fromUrl :: String -> Maybe Integer -> Key
diff --git a/Backend/WORM.hs b/Backend/WORM.hs
index 5232037136..3471eedc14 100644
--- a/Backend/WORM.hs
+++ b/Backend/WORM.hs
@@ -20,6 +20,7 @@ backend = Backend
 	{ name = "WORM"
 	, getKey = keyValue
 	, fsckKey = Nothing
+	, canUpgradeKey = Nothing
 	}
 
 {- The key includes the file size, modification time, and the
diff --git a/Command/Migrate.hs b/Command/Migrate.hs
index 0b23c2a400..d486eeb09c 100644
--- a/Command/Migrate.hs
+++ b/Command/Migrate.hs
@@ -11,6 +11,7 @@ import Common.Annex
 import Command
 import Backend
 import qualified Types.Key
+import qualified Types.Backend
 import Types.KeySource
 import Annex.Content
 import qualified Command.ReKey
@@ -26,7 +27,7 @@ start :: FilePath -> (Key, Backend) -> CommandStart
 start file (key, oldbackend) = do
 	exists <- inAnnex key
 	newbackend <- choosebackend =<< chooseBackend file
-	if (newbackend /= oldbackend || upgradableKey key) && exists
+	if (newbackend /= oldbackend || upgradableKey oldbackend key) && exists
 		then do
 			showStart "migrate" file
 			next $ perform file key oldbackend newbackend
@@ -35,10 +36,17 @@ start file (key, oldbackend) = do
 	choosebackend Nothing = Prelude.head <$> orderedList
 	choosebackend (Just backend) = return backend
 
-{- Checks if a key is upgradable to a newer representation. -}
-{- Ideally, all keys have file size metadata. Old keys may not. -}
-upgradableKey :: Key -> Bool
-upgradableKey key = isNothing $ Types.Key.keySize key
+{- Checks if a key is upgradable to a newer representation.
+ - 
+ - Reasons for migration:
+ -  - Ideally, all keys have file size metadata. Old keys may not.
+ -  - Something has changed in the backend, such as a bug fix.
+ -}
+upgradableKey :: Backend -> Key -> Bool
+upgradableKey backend key = isNothing (Types.Key.keySize key) || backendupgradable
+  where
+	backendupgradable = maybe False (\a -> a key)
+		(Types.Backend.canUpgradeKey backend)
 
 {- Store the old backend's key in the new backend
  - The old backend's key is not dropped from it, because there may
diff --git a/Types/Backend.hs b/Types/Backend.hs
index d79787c27c..c7d962db06 100644
--- a/Types/Backend.hs
+++ b/Types/Backend.hs
@@ -16,6 +16,7 @@ data BackendA a = Backend
 	{ name :: String
 	, getKey :: KeySource -> a (Maybe Key) 
 	, fsckKey :: Maybe (Key -> FilePath -> a Bool)
+	, canUpgradeKey :: Maybe (Key -> Bool)
 	}
 
 instance Show (BackendA a) where
diff --git a/debian/changelog b/debian/changelog
index ab3f6f14b8..e390adf27d 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -10,6 +10,11 @@ git-annex (3.20121212) UNRELEASED; urgency=low
   * Bugfix: Fixed bug parsing transfer info files, where the newline after
     the filename was included in it. This was generally benign, but in
     the assistant, it caused unexpected dropping of preferred content.
+  * Bugfix: Remove leading \ from checksums output by sha*sum commands,
+    when the filename contains \ or a newline. Closes: #696384
+  * fsck: Still accept checksums with a leading \ as valid, now that
+    above bug is fixed.
+  * migrate: Remove leading \ in checksums.
 
  -- Joey Hess <joeyh@debian.org>  Thu, 13 Dec 2012 14:06:43 -0400