diff --git a/Logs/Difference/Pure.hs b/Logs/Difference/Pure.hs
index bbd4d348df..25f3844d60 100644
--- a/Logs/Difference/Pure.hs
+++ b/Logs/Difference/Pure.hs
@@ -18,8 +18,7 @@ import Types.Difference
 import Logs.UUIDBased
 
 parseDifferencesLog :: String -> (M.Map UUID Differences)
-parseDifferencesLog = simpleMap 
-	. parseLog (Just . maybe UnknownDifferences Differences . readish)
+parseDifferencesLog = simpleMap . parseLog (Just . readDifferences)
 
 -- The sum of all recorded differences, across all UUIDs.
 allDifferences :: M.Map UUID Differences -> Differences
diff --git a/Types/Difference.hs b/Types/Difference.hs
index f92a307363..e4562a0d68 100644
--- a/Types/Difference.hs
+++ b/Types/Difference.hs
@@ -8,12 +8,14 @@
 module Types.Difference (
 	Difference(..),
 	Differences(..),
+	readDifferences,
 	getDifferences,
 	differenceConfigKey,
 	differenceConfigVal,
 	hasDifference,
 ) where
 
+import Utility.PartialPrelude
 import qualified Git
 import qualified Git.Config
 
@@ -55,9 +57,13 @@ instance Monoid Differences where
 	mappend (Differences l1) (Differences l2) = Differences (canon (l1 ++ l2))
 	mappend _ _ = UnknownDifferences
 
+-- Canonical form, allowing comparison.
 canon :: [Difference] -> [Difference]
 canon = nub . sort
 
+readDifferences :: String -> Differences
+readDifferences = maybe UnknownDifferences Differences . readish
+
 getDifferences :: Git.Repo -> Differences
 getDifferences r = Differences $ catMaybes $
 	map getmaybe [minBound .. maxBound]