DateTimeSelector does not create proper name attribute for new records

Rails 3.0.1

I am using time_select in a dynamically create field with field_for and the prefix it creates for a new object is missing the empty index array. The attribute it creates is: name="day[new_rule_attributes][start(1i)]" but it should be name="day[new_rule_attributes][][start(1i)]". This would be consistent with other fields generated the same way. For example, on the same form f.text_field creates name="day[new_rule_attributes][][action]".

The cause appears to be in the private function input_name_from_type in date_helper.rb:

def input_name_from_type(type)
  prefix = @options[:prefix] || ActionView::Helpers::DateTimeSelector::DEFAULT_PREFIX
  prefix += "[#{@options[:index]}]" if @options.has_key?(:index)

  field_name = @options[:field_name] || type
  if @options[:include_position]
    field_name += "(#{ActionView::Helpers::DateTimeSelector::POSITION[type]}i)"
  end

  @options[:discard_type] ? prefix : "#{prefix}[#{field_name}]"
end

In line 866 (3rd line above) the array is only added if the object has a key (set somewhere earlier). Shouldn't the proper behaviour be to add an empty array if there was no key?