diff --git a/src/Patch.hs b/src/Patch.hs
index c6e7aa627..8c38c0939 100644
--- a/src/Patch.hs
+++ b/src/Patch.hs
@@ -5,7 +5,6 @@ module Patch
 , after
 , before
 , unPatch
-, patchSum
 , maybeFst
 , maybeSnd
 , mapPatch
@@ -47,10 +46,6 @@ mapPatch f _ (Delete  a  ) = Delete  (f a)
 mapPatch _ g (Insert    b) = Insert  (g b)
 mapPatch f g (Replace a b) = Replace (f a) (g b)
 
--- | Calculate the cost of the patch given a function to compute the cost of a item.
-patchSum :: (a -> Int) -> Patch a -> Int
-patchSum termCost patch = maybe 0 termCost (before patch) + maybe 0 termCost (after patch)
-
 -- | Return Just the value in This, or the first value in These, if any.
 maybeFst :: These a b -> Maybe a
 maybeFst = these Just (const Nothing) ((Just .) . const)