src/Pure/Isar/keyword.scala

--- a/src/Pure/Isar/keyword.scala	Wed Aug 03 11:45:09 2016 +0200
+++ b/src/Pure/Isar/keyword.scala	Thu Aug 04 10:55:51 2016 +0200
@@ -87,6 +87,8 @@
   val proof_close = qed + PRF_CLOSE
   val proof_enclose = Set(PRF_BLOCK, NEXT_BLOCK, QED_BLOCK, PRF_CLOSE)
 
+  val close_structure = Set(NEXT_BLOCK, QED_BLOCK, PRF_CLOSE, THY_END)
+
 
 
   /** keyword tables **/