--- a/Nominal/Parser.thy	Thu Mar 11 19:43:50 2010 +0100
+++ b/Nominal/Parser.thy	Thu Mar 11 20:49:31 2010 +0100
@@ -413,11 +413,11 @@
     [Attrib.internal (fn _ => Nominal_ThmDecls.eqvt_add)]), q_eqvt) lthy19;
   val supports = map (prove_supports lthy20 q_perm) consts
   val _ = map tracing (map PolyML.makestring supports);
-  val fin_supp = HOLogic.conj_elims (prove_fs lthy20 q_induct supports q_tys);
+  val fin_supp = HOLogic.conj_elims (prove_fs lthy20 q_induct supports q_tys) handle _ => []
   val thy3 = Local_Theory.exit_global lthy20;
   val lthy21 = Theory_Target.instantiation (qty_full_names, [], @{sort fs}) thy3;
   fun tac _ = Class.intro_classes_tac [] THEN (ALLGOALS (resolve_tac fin_supp))
-  val lthy22 = Class.prove_instantiation_instance tac lthy21;
+  val lthy22 = Class.prove_instantiation_instance tac lthy21 handle _ => lthy20
 in
   ((raw_dt_names, raw_bn_funs, raw_bn_eqs, raw_binds), lthy22)
 end