src/Pure/Isar/attrib.ML

 
 (* internal attribute *)
 
 fun internal att =
   Token.make_src ("Pure.attribute", Position.none)
-    [Token.make_value "<attribute>" (Token.Attribute att)];
+    [Token.make_string ("<attribute>", Position.none) |> Token.assign (SOME (Token.Attribute att))];
 
 val _ = Theory.setup
   (setup (Binding.make ("attribute", @{here}))
     (Scan.lift Args.internal_attribute >> Morphism.form)
     "internal attribute");