diff -r ccf2df82b2d3 -r d273c24b5776 src/Pure/drule.ML
--- a/src/Pure/drule.ML	Tue Dec 15 16:01:57 2015 +0100
+++ b/src/Pure/drule.ML	Tue Dec 15 16:57:10 2015 +0100
@@ -94,6 +94,7 @@
   val cterm_add_frees: cterm -> cterm list -> cterm list
   val cterm_add_vars: cterm -> cterm list -> cterm list
   val dummy_thm: thm
+  val free_dummy_thm: thm
   val is_sort_constraint: term -> bool
   val sort_constraintI: thm
   val sort_constraint_eq: thm
@@ -628,6 +629,7 @@
 val cterm_add_vars = Thm.add_vars o mk_term;
 
 val dummy_thm = mk_term (certify Term.dummy_prop);
+val free_dummy_thm = Thm.tag_free_dummy dummy_thm;
 
 
 (* sort_constraint *)