diff --git a/ChangeLog b/ChangeLog
index dba9767c34..7e8222a313 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Sep 17 08:30:27 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/tracer.rb: count only non-internal libraries in stack trace,
+	  ignoring custom_require.  [ruby-core:31858]
+
 Fri Sep 17 02:18:41 2010  Akinori MUSHA  <knu@iDaemons.org>
 
 	* tool/mkconfig.rb: Fix build with m4 1.4.15 generating duplicate
diff --git a/lib/tracer.rb b/lib/tracer.rb
index a0b4fdf133..318b254ac8 100644
--- a/lib/tracer.rb
+++ b/lib/tracer.rb
@@ -190,6 +190,6 @@ if $0 == __FILE__
   ARGV.shift
   Tracer.on
   require $0
-elsif caller.size <= 1 
+elsif caller.count {|bt| /\A<internal:[^<>]+>:/ !~ bt} <= 1
   Tracer.on
 end