src/Pure/Isar/attrib.ML

 
 fun setup binding scan comment = define_global binding (attribute_syntax scan) comment #> snd;
 fun local_setup binding scan comment = define binding (attribute_syntax scan) comment #> snd;
 
 fun attribute_setup name source comment =
-  ML_Lex.read_source false source
+  ML_Lex.read_source source
   |> ML_Context.expression (Input.range_of source) "parser" "Thm.attribute context_parser"
     ("Context.map_proof (Attrib.local_setup " ^ ML_Syntax.atomic (ML_Syntax.make_binding name) ^
       " parser " ^ ML_Syntax.print_string comment ^ ")")
   |> Context.proof_map;