diff --git a/ChangeLog b/ChangeLog
index 7e0d62565a..0cfd894884 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Sep 18 20:37:59 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/optparse.rb (OptionParser::ParseError#set_backtrace): omits
+	  OptionParser internal backtraces unless debug flag is set.
+
 Thu Sep 18 20:02:48 2008  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* lib/uri/common.rb (unescape): skip '%' to make String#hex work
diff --git a/lib/optparse.rb b/lib/optparse.rb
index 86681235a0..aef3c0d486 100644
--- a/lib/optparse.rb
+++ b/lib/optparse.rb
@@ -1605,6 +1605,13 @@ class OptionParser
       argv
     end
 
+    def set_backtrace(array)
+      unless $DEBUG
+        array.delete_if(&%r"\A#{Regexp.quote(__FILE__)}:"o.method(:=~))
+      end
+      super(array)
+    end
+
     def set_option(opt, eq)
       if eq
         @args[0] = opt