error missed by validator--tag not closed

I recently ran a page with a fragment like this through the validator:
  <img src="x.png" alt="y"
(with no closing ">")

This passes as valid, which I don't think it is.  The HTMLHelp validator
flags it as an error.

A complete source page that demonstrates this:
  http://www.cs.sfu.ca/~ggbaker/test/validerror.html

The validator output for this page:
http://validator.w3.org/check?uri=http%3A%2F%2Fwww.cs.sfu.ca%2F%7Eggbaker%2Ftest%2Fvaliderror.html&charset=iso-8859-1+%28Western+Europe%29&doctype=%28detect+automatically%29&ss=1&verbose=1

Am I right that this is a bug in the validator?

Greg Baker, Lecturer
School of Computing Science
Simon Fraser University
Burnaby, BC, V5A 1S6
E-mail: ggbaker@cs.sfu.ca