src/Pure/System/session.scala

 
       def id_command(command: Command)
       {
         if (!global_state().defined_command(command.id)) {
           global_state.change(_.define_command(command))
-          prover.get.define_command(command.id, Symbol.encode(command.source))
+          prover.get.define_command(command)
         }
       }
       doc_edits foreach {
         case (_, edit) =>
           edit foreach { case (c1, c2) => c1 foreach id_command; c2 foreach id_command }