src/Pure/PIDE/protocol.scala

     protocol_command("Prover.init_session_base",
       encode_sessions(resources.sessions_structure.session_positions),
       encode_table(resources.sessions_structure.dest_session_directories),
       encode_list(base.doc_names),
       encode_table(base.global_theories.toList),
-      encode_list(base.loaded_theories.keys),
-      encode_table(base.dest_known_theories))
+      encode_list(base.loaded_theories.keys))
   }
 
 
   /* interned items */