src/Pure/Isar/attrib.ML

--- a/src/Pure/Isar/attrib.ML	Fri Apr 30 17:59:36 1999 +0200
+++ b/src/Pure/Isar/attrib.ML	Fri Apr 30 18:01:11 1999 +0200
@@ -50,6 +50,7 @@
          * string) * stamp) Symtab.table};
 
   val empty = {space = NameSpace.empty, attrs = Symtab.empty};
+  val copy = I;
   val prep_ext = I;
 
   fun merge ({space = space1, attrs = attrs1}, {space = space2, attrs = attrs2}) =