src/Pure/theory.ML

 
 (* join theory *)
 
 fun join_theory [] = raise List.Empty
   | join_theory [thy] = thy
-  | join_theory thys = foldl1 Context.join_thys thys |> Sign.restore_naming (hd thys);
+  | join_theory thys = foldl1 Context.join_thys thys;
 
 
 (* begin/end theory *)
 
 val begin_wrappers = rev o #1 o #wrappers o rep_theory;

       val thy = Context.begin_thy name imports;
       val wrappers = begin_wrappers thy;
     in
       thy
       |> init_markup (name, pos)
+      |> Sign.init_naming
       |> Sign.local_path
-      |> Sign.theory_naming
       |> apply_wrappers wrappers
       |> tap (Syntax.force_syntax o Sign.syn_of)
     end;
 
 fun end_theory thy =