diff -r 4c7fdc00bd59 -r 92fda7beace4 src/Pure/PIDE/command.ML
--- a/src/Pure/PIDE/command.ML	Wed Apr 03 16:45:14 2013 +0200
+++ b/src/Pure/PIDE/command.ML	Wed Apr 03 20:38:50 2013 +0200
@@ -63,8 +63,9 @@
 
 fun run int tr st =
   if Goal.future_enabled () andalso Keyword.is_diag (Toplevel.name_of tr) then
-    (Goal.fork_name "Toplevel.diag" ~1 (fn () => Toplevel.command_exception int tr st);
-      ([], SOME st))
+    Toplevel.setmp_thread_position tr (fn () =>
+      (Goal.fork_name "Toplevel.diag" ~1 (fn () => Toplevel.command_exception int tr st);
+        ([], SOME st))) ()
   else Toplevel.command_errors int tr st;
 
 fun check_cmts tr cmts st =