diff --git a/ChangeLog b/ChangeLog
index 6559cc8954..81c42816d9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Mar  7 10:40:49 2013  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* tool/change_maker.rb (#diff2index): check Encoding::BINARY.
+	  BASERUBY may still be 1.8.x.
+
 Thu Mar  7 08:47:42 2013  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* NEWS (Mutex#owned?): no longer experimental.
diff --git a/tool/change_maker.rb b/tool/change_maker.rb
index 3cf9dd663a..2bbc275d93 100755
--- a/tool/change_maker.rb
+++ b/tool/change_maker.rb
@@ -4,7 +4,9 @@ def diff2index(cmd, *argv)
   lines = []
   path = nil
   output = `#{cmd} #{argv.join(" ")}`
-  output.force_encoding Encoding::BINARY
+  if defined? Encoding::BINARY
+    output.force_encoding Encoding::BINARY
+  end
   output.each_line do |line|
     case line
     when /^Index: (\S*)/, /^diff --git [a-z]\/(\S*) [a-z]\/\1/