diff -r b9a6b465da25 -r 774df7c59508 src/Pure/Proof/extraction.ML
--- a/src/Pure/Proof/extraction.ML	Sun Apr 17 13:47:22 2011 +0200
+++ b/src/Pure/Proof/extraction.ML	Sun Apr 17 19:54:04 2011 +0200
@@ -36,7 +36,7 @@
   thy
   |> Theory.copy
   |> Sign.root_path
-  |> Sign.add_types [(Binding.name "Type", 0, NoSyn), (Binding.name "Null", 0, NoSyn)]
+  |> Sign.add_types_global [(Binding.name "Type", 0, NoSyn), (Binding.name "Null", 0, NoSyn)]
   |> Sign.add_consts
       [(Binding.name "typeof", "'b::{} => Type", NoSyn),
        (Binding.name "Type", "'a::{} itself => Type", NoSyn),