
diff -r 6c558efcc754 -r da548623916a src/HOL/Unix/Unix.thy
--- a/src/HOL/Unix/Unix.thy	Tue Dec 20 22:06:00 2005 +0100
+++ b/src/HOL/Unix/Unix.thy	Wed Dec 21 12:02:57 2005 +0100
@@ -1058,7 +1058,8 @@
               have "lookup root ((path @ [y]) @ (us @ [u])) \<noteq> None \<or>
                   lookup root ((path @ [y]) @ us) \<noteq> None"
                 by cases (auto dest: access_some_lookup)
-              then show ?thesis by (blast dest!: lookup_some_append)
+              then show ?thesis 
+                by (simp add: not_None_eq, blast dest!: lookup_some_append)
             qed
             finally show ?thesis .
           qed




