diff -r 25af24e1f37b -r 180f1b3508ed src/HOL/Unix/Nested_Environment.thy
--- a/src/HOL/Unix/Nested_Environment.thy	Tue Sep 09 17:51:07 2014 +0200
+++ b/src/HOL/Unix/Nested_Environment.thy	Tue Sep 09 20:51:36 2014 +0200
@@ -19,7 +19,7 @@
   position within the structure.
 *}
 
-datatype ('a, 'b, 'c) env =
+datatype_new ('a, 'b, 'c) env =
     Val 'a
   | Env 'b  "'c \<Rightarrow> ('a, 'b, 'c) env option"