--- AnyEvent/lib/AnyEvent.pm	2009/07/21 03:30:02	1.252
+++ AnyEvent/lib/AnyEvent.pm	2009/07/21 06:00:47	1.253
@@ -1154,7 +1154,7 @@
    if ($MODEL) {
       $cb->();
 
-      1
+      undef
    } else {
       push @post_detect, $cb;