diff --git a/ChangeLog b/ChangeLog
index 0a1909ee1d..6ee79fd8c0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Fri Sep  2 04:05:25 2011  Aaron Patterson <aaron@tenderlovemaking.com>
+
+	* ext/psych/lib/psych/visitors/yaml_tree.rb: emit strings tagged as
+	  ascii-8bit as binary in YAML.
+	* test/psych/test_string.rb: corresponding test.
+
 Fri Sep  2 01:07:14 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* numeric.c (flo_round): substitute machine dependent magic number.
diff --git a/ext/psych/lib/psych/visitors/yaml_tree.rb b/ext/psych/lib/psych/visitors/yaml_tree.rb
index eef6125ff1..70db181a95 100644
--- a/ext/psych/lib/psych/visitors/yaml_tree.rb
+++ b/ext/psych/lib/psych/visitors/yaml_tree.rb
@@ -214,12 +214,19 @@ module Psych
         end
       end
 
+      def binary? string
+        string.encoding == Encoding::ASCII_8BIT ||
+          string.index("\x00") ||
+          string.count("\x00-\x7F", "^ -~\t\r\n").fdiv(string.length) > 0.3
+      end
+      private :binary?
+
       def visit_String o
         plain = false
         quote = false
         style = Nodes::Scalar::ANY
 
-        if o.index("\x00") || o.count("\x00-\x7F", "^ -~\t\r\n").fdiv(o.length) > 0.3
+        if binary?(o)
           str   = [o].pack('m').chomp
           tag   = '!binary' # FIXME: change to below when syck is removed
           #tag   = 'tag:yaml.org,2002:binary'
diff --git a/test/psych/test_string.rb b/test/psych/test_string.rb
index 96d77e0f42..51f1280abf 100644
--- a/test/psych/test_string.rb
+++ b/test/psych/test_string.rb
@@ -2,6 +2,14 @@ require 'psych/helper'
 
 module Psych
   class TestString < TestCase
+    def test_tagged_binary_should_be_dumped_as_binary
+      string = "hello world!"
+      string.force_encoding 'ascii-8bit'
+      yml = Psych.dump string
+      assert_match(/binary/, yml)
+      assert_equal string, Psych.load(yml)
+    end
+
     def test_binary_string_null
       string = "\x00"
       yml = Psych.dump string