diff -r 2386fb64feaf -r dde7df1176b7 src/HOL/Nominal/Examples/W.thy
--- a/src/HOL/Nominal/Examples/W.thy	Thu Mar 03 22:06:15 2011 +0100
+++ b/src/HOL/Nominal/Examples/W.thy	Fri Mar 04 00:09:47 2011 +0100
@@ -433,7 +433,7 @@
   assumes "x \<in> S"
   and     "S \<sharp>* z"
   shows  "x \<sharp> z"
-using prems  by (simp add: fresh_star_def)
+using assms by (simp add: fresh_star_def)
 
 lemma fresh_gen_set:
   fixes X::"tvar"