using HTML Agility Pack to verify HTML not working for me

using HTML Agility Pack to verify HTML not working for me

not sure if I'm missing some option, but <div><b>hello</div> says it's ok
(no errors), this is the code (vb) ...
Dim htmlDoc = New HtmlDocument()
htmlDoc.Loadhtml("<div><b>hello</div>")
htmlDoc.ParseErrors.count is 0
Am I missing setting an option or something?
PD: I tried htmlDoc.Loadhtml("<b>hello") and that does return as invalid,
not sure why the unclosed <b> inside the <div> doesn't. (I originally
posted this in the "code review" site and they said this belonged to Stack
Overflow)