diff -r 34bc296374ee -r 59258a3192bf src/HOL/Tools/Lifting/lifting_util.ML
--- a/src/HOL/Tools/Lifting/lifting_util.ML	Tue Jun 04 15:14:19 2019 +0200
+++ b/src/HOL/Tools/Lifting/lifting_util.ML	Tue Jun 04 15:14:56 2019 +0200
@@ -128,7 +128,6 @@
   end
 
 fun conceal_naming_result f lthy = 
-  let val old_lthy = lthy
-  in lthy |> Proof_Context.concealed |> f ||> Proof_Context.restore_naming old_lthy end;
+  lthy |> Proof_Context.concealed |> f ||> Proof_Context.restore_naming lthy;
 
 end