HtmlAgilityPack invalid markup

I am using the HtmlAgilityPack from codeplex. When I pass a simple html string into it and then get the resulting html back, it cuts off tags.

Example:

string html = "<select><option>test</option></select>";
HtmlDocument document = new HtmlDocument();
document.LoadHtml(html);

var result = d.DocumentNode.OuterHtml;

// result gives me:
<select><option>test</select>

So the closing tag for the option is missing. Am I missing a setting or using this wrong?