diff --git a/ChangeLog b/ChangeLog
index 790e4bc0cc..81ffc84791 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Oct 12 15:14:21 2010  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* io.c (rb_io_putc): support multibyte characters.
+	  [ruby-core:30697]
+
 Tue Oct 12 15:10:31 2010  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* numeric.c (rb_enc_uint_chr): split from int_chr.
diff --git a/NEWS b/NEWS
index d6c7e39dfa..2d6e6df552 100644
--- a/NEWS
+++ b/NEWS
@@ -40,6 +40,10 @@ with all sufficient information, see the ChangeLog file.
     * extended methods:
       * Time#strftime supports %:z and %::z.
 
+  * IO
+    * extended methods:
+      * IO#putc supports multibyte characters
+
 * io/console
   * new methods:
     * IO#noecho {|io| }
diff --git a/io.c b/io.c
index 7255fc46f4..7625796b2b 100644
--- a/io.c
+++ b/io.c
@@ -6053,9 +6053,15 @@ rb_f_print(int argc, VALUE *argv)
 static VALUE
 rb_io_putc(VALUE io, VALUE ch)
 {
-    char c = NUM2CHR(ch);
-
-    rb_io_write(io, rb_str_new(&c, 1));
+    VALUE str;
+    if (TYPE(ch) == T_STRING) {
+	str = rb_str_substr(ch, 0, 1);
+    }
+    else {
+	char c = NUM2CHR(ch);
+	str = rb_str_new(&c, 1);
+    }
+    rb_io_write(io, str);
     return ch;
 }
 
diff --git a/test/ruby/test_io_m17n.rb b/test/ruby/test_io_m17n.rb
index 3d3b64c6cc..5f35c227ea 100644
--- a/test/ruby/test_io_m17n.rb
+++ b/test/ruby/test_io_m17n.rb
@@ -1026,6 +1026,16 @@ EOT
     }
   end
 
+  def test_open_pipe_r_enc2
+    open("|#{EnvUtil.rubybin} -e 'putc ?\u3042'", "r:UTF-8") {|f|
+      assert_equal(Encoding::UTF_8, f.external_encoding)
+      assert_equal(nil, f.internal_encoding)
+      s = f.read
+      assert_equal(Encoding::UTF_8, s.encoding)
+      assert_equal("\u3042", s)
+    }
+  end
+
   def test_s_foreach_enc
     with_tmpdir {
       generate_file("t", "\xff")