diff -r b28defd0b5a5 -r db75b4005d9a src/HOL/Typerep.thy
--- a/src/HOL/Typerep.thy	Mon Jul 16 15:57:21 2012 +0200
+++ b/src/HOL/Typerep.thy	Mon Jul 16 21:20:56 2012 +0200
@@ -64,8 +64,8 @@
   end;
 
 fun ensure_typerep tyco thy =
-  if not (can (Sorts.mg_domain (Sign.classes_of thy) tyco) @{sort typerep})
-    andalso can (Sorts.mg_domain (Sign.classes_of thy) tyco) @{sort type}
+  if not (Sorts.has_instance (Sign.classes_of thy) tyco @{sort typerep})
+    andalso Sorts.has_instance (Sign.classes_of thy) tyco @{sort type}
   then add_typerep tyco thy else thy;
 
 in