diff --git a/src/Diffing/Interpreter.hs b/src/Diffing/Interpreter.hs
index 0359952da..f16a07923 100644
--- a/src/Diffing/Interpreter.hs
+++ b/src/Diffing/Interpreter.hs
@@ -1,6 +1,7 @@
-{-# LANGUAGE FunctionalDependencies, GeneralizedNewtypeDeriving, TypeOperators, UndecidableInstances #-}
+{-# LANGUAGE FunctionalDependencies, GeneralizedNewtypeDeriving, TypeFamilyDependencies, TypeOperators, UndecidableInstances #-}
 module Diffing.Interpreter
 ( diffTerms
+, HasDiffFor(..)
 , DiffTerms(..)
 , stripDiff
 ) where
@@ -29,10 +30,16 @@ stripDiff :: Functor syntax
           -> Diff.Diff syntax ann1 ann2
 stripDiff = bimap snd snd
 
+class HasDiffFor (term :: * -> *) where
+  type DiffFor term = (res :: * -> * -> *) | res -> term
+
 class DiffTerms term diff | diff -> term, term -> diff where
   -- | Diff a 'These' of terms.
   diffTermPair :: These (term ann1) (term ann2) -> diff ann1 ann2
 
+instance HasDiffFor (Term syntax) where
+  type DiffFor (Term syntax) = Diff.Diff syntax
+
 instance (Diffable syntax, Eq1 syntax, Hashable1 syntax, Traversable syntax) => DiffTerms (Term syntax) (Diff.Diff syntax) where
   diffTermPair = these Diff.deleting Diff.inserting diffTerms