diff -r 3e08311ada8e -r 5c4800f6b25a src/Pure/Tools/build.ML
--- a/src/Pure/Tools/build.ML	Mon Jul 06 16:52:48 2020 +0200
+++ b/src/Pure/Tools/build.ML	Wed Jul 08 14:43:02 2020 +0200
@@ -58,7 +58,7 @@
 
     val timing_props =
       [("threads", threads)] @ Markup.timing_properties timing @ [("factor", factor)];
-    val _ = Protocol_Message.marker "Timing" timing_props;
+    val _ = Output.protocol_message (Markup.session_timing :: timing_props) [];
     val _ =
       if verbose then
         Output.physical_stderr ("Timing " ^ session_name ^ " (" ^
@@ -93,6 +93,8 @@
         end
       else if function = Markup.theory_timing then
         Protocol_Message.marker (#2 function) args
+      else if function = Markup.session_timing then
+        Protocol_Message.marker "Timing" args
       else
         (case Markup.dest_loading_theory props of
           SOME name => Protocol_Message.marker_text "loading_theory" name