src/Pure/Thy/thy_syntax.scala

--- a/src/Pure/Thy/thy_syntax.scala	Fri Mar 16 20:45:47 2012 +0100
+++ b/src/Pure/Thy/thy_syntax.scala	Fri Mar 16 21:20:23 2012 +0100
@@ -57,8 +57,8 @@
       {
         syntax.heading_level(command) match {
           case Some(i) =>
-            close(_ >= i)
-            stack = (i, command.source, buffer()) :: stack
+            close(_ > i)
+            stack = (i + 1, command.source, buffer()) :: stack
           case None =>
         }
         stack.head._3 += Atom(command)