diff -r d57da4abb47d -r e1b61c5fd494 src/HOL/TLA/Action.thy
--- a/src/HOL/TLA/Action.thy	Tue Feb 23 10:11:15 2010 +0100
+++ b/src/HOL/TLA/Action.thy	Tue Feb 23 10:11:16 2010 +0100
@@ -16,8 +16,8 @@
   'a trfun = "(state * state) => 'a"
   action   = "bool trfun"
 
-instance
-  "*" :: (world, world) world ..
+arities
+  "*" :: (world, world) world
 
 consts
   (** abstract syntax **)