CSS selector problem with Mojo::DOM and dd

gistfile1.pl

#!/usr/bin/perl

use strict;
use warnings;

use Test::More tests => 2;
use Mojo::DOM;

# passes
{
my $dom = Mojo::DOM->new(<<'ENDOFHTML');
<p>
  <b>bold</b>
  <i>italic</i>
</div>
ENDOFHTML
is $dom->at("b + i")->text, "italic";
}

# passes
{
my $dom = Mojo::DOM->new(<<'ENDOFHTML');
<dl>
  <dt>term</dt>
  <dd>description</dd>
</dl>
ENDOFHTML
is $dom->at("dt + dd")->text, "description";
}

# fails
{
my $dom = Mojo::DOM->new(<<'ENDOFHTML');
<dl>
  <dt>term</dt>
  <dd>
    <dl>
      <dt>term 2</dt>
      <dd>description</dd>
    </dl>
  </dd>
</dl>
ENDOFHTML
is $dom->at("dt + dd")->text, "description";
}

__END__
1..2
ok 1
ok 2
not ok 3
#   Failed test at /tmp/barney.pl line 42.
#          got: ''
#     expected: 'description'
# Looks like you planned 2 tests but ran 3.
# Looks like you failed 1 test of 3 run.