diff --git a/actionpack/CHANGELOG b/actionpack/CHANGELOG
index e758983d7a..aab26b411c 100644
--- a/actionpack/CHANGELOG
+++ b/actionpack/CHANGELOG
@@ -1,5 +1,7 @@
 *Edge*
 
+* Ruby 1.9: fix Content-Length for multibyte send_data streaming.  #2661 [Sava Chankov]
+
 * Ruby 1.9: ERB template encoding using a magic comment at the top of the file.  [Jeremy Kemper]
     <%# encoding: utf-8 %>
 
diff --git a/actionpack/lib/action_controller/base/streaming.rb b/actionpack/lib/action_controller/base/streaming.rb
index 9ff4f25f43..f52810ff3a 100644
--- a/actionpack/lib/action_controller/base/streaming.rb
+++ b/actionpack/lib/action_controller/base/streaming.rb
@@ -1,3 +1,5 @@
+require 'active_support/core_ext/string/bytesize'
+
 module ActionController #:nodoc:
   # Methods for sending arbitrary data and for streaming files to the browser,
   # instead of rendering.
@@ -142,7 +144,7 @@ module ActionController #:nodoc:
       # instead. See ActionController::Base#render for more information.
       def send_data(data, options = {}) #:doc:
         logger.info "Sending data #{options[:filename]}" if logger
-        send_file_headers! options.merge(:length => data.size)
+        send_file_headers! options.merge(:length => data.bytesize)
         @performed_render = false
         render :status => options[:status], :text => data
       end
diff --git a/actionpack/test/controller/send_file_test.rb b/actionpack/test/controller/send_file_test.rb
index ae32ee5649..154daad1b9 100644
--- a/actionpack/test/controller/send_file_test.rb
+++ b/actionpack/test/controller/send_file_test.rb
@@ -1,3 +1,4 @@
+# encoding: utf-8
 require 'abstract_unit'
 
 module TestFileUtils
@@ -22,6 +23,10 @@ class SendFileController < ActionController::Base
   def data
     send_data(file_data, options)
   end
+
+  def multibyte_text_data
+    send_data("Кирилица\n祝您好運", options)
+  end
 end
 
 class SendFileTest < ActionController::TestCase
@@ -163,4 +168,11 @@ class SendFileTest < ActionController::TestCase
       assert_equal 200, @response.status
     end
   end
+
+  def test_send_data_content_length_header
+    @controller.headers = {}
+    @controller.options = { :type => :text, :filename => 'file_with_utf8_text' }
+    process('multibyte_text_data')
+    assert_equal '29', @controller.headers['Content-Length']
+  end
 end