diff --git a/ChangeLog b/ChangeLog
index 966b72fcbb..de652b2497 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sun Apr  8 07:26:40 2012  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* lib/webrick/utils.rb (WEBrick::Utils::TimeoutHandler): get keys
+	  and fetch values from it to prevent @timeout_info's error
+	  "can't add a new key into hash during iteration".
+
 Sun Apr  8 06:51:57 2012  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* io.c (io_unread): cast as long the value for extra_max.
diff --git a/lib/webrick/utils.rb b/lib/webrick/utils.rb
index d9c39360ee..eab2375968 100644
--- a/lib/webrick/utils.rb
+++ b/lib/webrick/utils.rb
@@ -175,7 +175,9 @@ module WEBrick
         Thread.start{
           while true
             now = Time.now
-            @timeout_info.dup.each{|thread, ary|
+            @timeout_info.keys.each{|thread|
+              ary = @timeout_info[thread]
+              next unless ary
               ary.dup.each{|info|
                 time, exception = *info
                 interrupt(thread, info.object_id, exception) if time < now