src/Pure/Isar/keyword.scala

--- a/src/Pure/Isar/keyword.scala	Sun Mar 17 20:03:55 2019 +0100
+++ b/src/Pure/Isar/keyword.scala	Sun Mar 17 21:26:42 2019 +0100
@@ -74,6 +74,8 @@
     Set(THY_LOAD, THY_DECL, THY_DECL_BLOCK, THY_DEFN, THY_STMT,
       THY_GOAL, THY_GOAL_DEFN, THY_GOAL_STMT)
 
+  val theory_defn = Set(THY_DEFN, THY_GOAL_DEFN)
+
   val prf_script = Set(PRF_SCRIPT)
 
   val proof =