diff --git a/src/Arguments.hs b/src/Arguments.hs
index 982d61f40..e13783843 100644
--- a/src/Arguments.hs
+++ b/src/Arguments.hs
@@ -3,39 +3,51 @@
 module Arguments where
 
 import Data.Maybe
-import Prelude
+import Data.Record
+import Data.String
+import Info
 import Prologue
 import Renderer
-import Info
+import Source
+import Syntax
+import Term
+import Text.Show
 
 
 data DiffMode = DiffCommits String String [FilePath] | DiffPaths FilePath FilePath
   deriving Show
 
 data DiffArguments where
-  DiffArguments :: (Monoid output, StringConv output ByteString) =>
-    { diffRenderer :: DiffRenderer DefaultFields output
+  DiffArguments :: (Monoid output, StringConv output ByteString, HasField fields Category, NFData (Record fields)) =>
+    { diffRenderer :: DiffRenderer fields output
+    , termDecorator :: Source -> Term (Syntax Text) (Record DefaultFields) -> Term (Syntax Text) (Record fields)
     , diffMode :: DiffMode
     , gitDir :: FilePath
     , alternateObjectDirs :: [FilePath]
     } -> DiffArguments
 
-deriving instance Show DiffArguments
+instance Show DiffArguments where
+  showsPrec d DiffArguments{..} = showParen (d > 10) $ showString "DiffArguments { " . foldr (.) identity (intersperse (showString ", ") fields) . showString " }"
+    where fields = [ showString "diffRenderer " . shows diffRenderer
+                   , showString "termDecorator _"
+                   , showString "diffMode " . shows diffMode
+                   , showString "gitDir " . shows gitDir
+                   , showString "alternateObjectDirs " . shows alternateObjectDirs ]
 
 patchDiff :: DiffMode -> FilePath -> [FilePath] -> DiffArguments
-patchDiff = DiffArguments PatchRenderer
+patchDiff = DiffArguments PatchRenderer (const identity)
 
 jsonDiff :: DiffMode -> FilePath -> [FilePath] -> DiffArguments
-jsonDiff = DiffArguments JSONDiffRenderer
+jsonDiff = DiffArguments JSONDiffRenderer (const identity)
 
 summaryDiff :: DiffMode -> FilePath -> [FilePath] -> DiffArguments
-summaryDiff = DiffArguments SummaryRenderer
+summaryDiff = DiffArguments SummaryRenderer (const identity)
 
 sExpressionDiff :: DiffMode -> FilePath -> [FilePath] -> DiffArguments
-sExpressionDiff = DiffArguments (SExpressionDiffRenderer TreeOnly)
+sExpressionDiff = DiffArguments (SExpressionDiffRenderer TreeOnly) (const identity)
 
 tocDiff :: DiffMode -> FilePath -> [FilePath] -> DiffArguments
-tocDiff = DiffArguments ToCRenderer
+tocDiff = DiffArguments ToCRenderer (const identity)
 
 
 data ParseMode = ParseCommit String [FilePath] | ParsePaths [FilePath]
diff --git a/src/SemanticCmdLine.hs b/src/SemanticCmdLine.hs
index c03549703..c1b1e9db2 100644
--- a/src/SemanticCmdLine.hs
+++ b/src/SemanticCmdLine.hs
@@ -49,7 +49,7 @@ runDiff DiffArguments{..} = do
   blobs <- runCommand $ case diffMode of
    DiffPaths a b -> pure <$> traverse readFile (both a b)
    DiffCommits sha1 sha2 paths -> readFilesAtSHAs gitDir alternateObjectDirs paths (both sha1 sha2)
-  Semantic.diffBlobPairs identity diffRenderer blobs
+  Semantic.diffBlobPairs termDecorator diffRenderer blobs
 
 runParse :: ParseArguments -> IO ByteString
 runParse ParseArguments{..} = do