Index: app/helpers/application_helper.rb
===================================================================
--- app/helpers/application_helper.rb	(revision 16661)
+++ app/helpers/application_helper.rb	(working copy)
@@ -198,7 +198,7 @@
     when 'Issue'
       object.visible? && html ? link_to_issue(object) : "##{object.id}"
     when 'Attachment'
-      html ? link_to_attachment(object, :download => true) : object.filename
+      html ? link_to_attachment(object) : object.filename
     when 'CustomValue', 'CustomFieldValue'
       if object.custom_field
         f = object.custom_field.format.formatted_custom_value(self, object, html)
Index: test/integration/lib/redmine/field_format/attachment_format_test.rb
===================================================================
--- test/integration/lib/redmine/field_format/attachment_format_test.rb	(revision 16661)
+++ test/integration/lib/redmine/field_format/attachment_format_test.rb	(working copy)
@@ -82,10 +82,10 @@
     assert_equal 1, link.size
     assert_equal "testfile.txt", link.text
 
-    # download the attachment
+    # preview the attachment
     get link.attr('href')
     assert_response :success
-    assert_equal "text/plain", response.content_type
+    assert_template :file
   end
 
   def test_create_without_attachment