Index: app/models/mail_handler.rb
===================================================================
--- app/models/mail_handler.rb	(revision 17805)
+++ app/models/mail_handler.rb	(working copy)
@@ -237,7 +237,7 @@
     end
 
     # ignore CLI-supplied defaults for new issues
-    handler_options[:issue].clear
+    handler_options[:issue] = {}
 
     journal = issue.init_journal(user)
     if from_journal && from_journal.private_notes?
Index: test/functional/mail_handler_controller_test.rb
===================================================================
--- test/functional/mail_handler_controller_test.rb	(revision 17805)
+++ test/functional/mail_handler_controller_test.rb	(working copy)
@@ -60,6 +60,20 @@
     assert_equal true, issue.is_private
   end
 
+  def test_should_update_issue
+    # Enable API and set a key
+    Setting.mail_handler_api_enabled = 1
+    Setting.mail_handler_api_key = 'secret'
+
+    assert_difference 'Journal.count' do
+      post :index, :params => {
+          :key => 'secret',
+          :email => IO.read(File.join(FIXTURES_PATH, 'ticket_reply.eml'))
+        }
+    end
+    assert_response 201
+  end
+
   def test_should_respond_with_422_if_not_created
     Project.find('onlinestore').destroy