diff --git a/src/PDF/Layer.hs b/src/PDF/Layer.hs
index 97e0f0b..0e6a696 100644
--- a/src/PDF/Layer.hs
+++ b/src/PDF/Layer.hs
@@ -65,13 +65,13 @@ unify = foldl complete emptyLayer
       }
 
 unifyDocStructure :: Structure -> Structure -> Structure
-unifyDocStructure update original = Structure {
-      xRef = Map.union (xRef update) (xRef original)
-    , trailer = Map.union (trailer update) (trailer original)
+unifyDocStructure new old = Structure {
+      xRef = Map.union (xRef new) (xRef old)
+    , trailer = Map.union (trailer new) (trailer old)
   }
 
 unifyOccurrences :: IndexedObjects -> [Occurrence] -> [Occurrence] -> [Occurrence]
-unifyOccurrences objects update = foldr addOlder update
+unifyOccurrences objects new = foldr addOlder new
   where
     addOlder occurrence@(Comment _) existing = occurrence : existing
     addOlder occurrence@(Indirect indirect) existing =