diff -r 91319c3d2841 -r a3cfe859d915 src/Pure/PIDE/protocol.scala
--- a/src/Pure/PIDE/protocol.scala	Mon Sep 16 15:30:38 2019 +0200
+++ b/src/Pure/PIDE/protocol.scala	Mon Sep 16 16:00:10 2019 +0200
@@ -245,8 +245,7 @@
       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))
   }