diff --git a/app/models/mail_handler.rb b/app/models/mail_handler.rb
index 8a5925cab..c6e3d8ff2 100644
--- a/app/models/mail_handler.rb
+++ b/app/models/mail_handler.rb
@@ -373,7 +373,8 @@ class MailHandler < ActionMailer::Base
       # try to reencode to utf8 manually with ruby1.8
       begin
         if h = email.header[:subject]
-          if m = h.value.match(/^=\?([^\?]+)\?/)
+          # http://tools.ietf.org/html/rfc2047#section-4
+          if m = h.value.match(/=\?([^\?]+)\?[BbQq]\?/)
             subject = Redmine::CodesetUtil.to_utf8(subject, m[1])
           end
         end
diff --git a/test/fixtures/mail_handler/subject_japanese_2.eml b/test/fixtures/mail_handler/subject_japanese_2.eml
new file mode 100644
index 000000000..d25d47863
--- /dev/null
+++ b/test/fixtures/mail_handler/subject_japanese_2.eml
@@ -0,0 +1,7 @@
+From: John Smith <JSmith@somenet.foo>
+To: "redmine@somenet.foo" <redmine@somenet.foo>
+Subject: Re: =?iso-2022-jp?b?GyRCJUYlOSVIGyhCCg=?=
+Date: Fri, 1 Jun 2012 14:39:38 +0200
+Message-ID: <87C31D42249DD0489D1A1444E3232DD7019D6183@foo.bar>
+
+Fixture
diff --git a/test/unit/mail_handler_test.rb b/test/unit/mail_handler_test.rb
index fd8e1404f..a0c5645d9 100644
--- a/test/unit/mail_handler_test.rb
+++ b/test/unit/mail_handler_test.rb
@@ -393,6 +393,17 @@ class MailHandlerTest < ActiveSupport::TestCase
     assert_equal ja, issue.subject
   end
 
+  def test_add_issue_with_mixed_japanese_subject
+    issue = submit_email(
+              'subject_japanese_2.eml',
+              :issue => {:project => 'ecookbook'}
+            )
+    assert_kind_of Issue, issue
+    ja = "Re: \xe3\x83\x86\xe3\x82\xb9\xe3\x83\x88"
+    ja.force_encoding('UTF-8') if ja.respond_to?(:force_encoding)
+    assert_equal ja, issue.subject
+  end
+
   def test_should_ignore_emails_from_locked_users
     User.find(2).lock!