src/Pure/PIDE/protocol.scala

--- a/src/Pure/PIDE/protocol.scala	Sat Dec 16 20:02:40 2017 +0100
+++ b/src/Pure/PIDE/protocol.scala	Sat Dec 16 21:53:07 2017 +0100
@@ -341,7 +341,8 @@
   def session_base(resources: Resources)
   {
     val base = resources.session_base.standard_path
-    protocol_command("Prover.session_base",
+    protocol_command("Prover.init_session_base",
+      encode_list(base.known.sessions.toList),
       encode_table(base.global_theories.toList),
       encode_list(base.loaded_theories.keys),
       encode_table(base.dest_known_theories))