--- a/Nominal-General/Nominal2_Atoms.thy	Thu May 13 17:41:28 2010 +0100
+++ b/Nominal-General/Nominal2_Atoms.thy	Thu May 13 18:19:48 2010 +0100
@@ -37,7 +37,7 @@
 lemma permute_flip_cancel2 [simp]: "(a \<leftrightarrow> b) \<bullet> (b \<leftrightarrow> a) \<bullet> x = x"
   by (simp add: flip_commute)
 
-lemma flip_eqvt: 
+lemma flip_eqvt[eqvt]: 
   fixes a b c::"'a::at_base"
   shows "p \<bullet> (a \<leftrightarrow> b) = (p \<bullet> a \<leftrightarrow> p \<bullet> b)"
   unfolding flip_def