Markdown does not render <p> tags with "HTML filter" turned on.

Whether I arrange the "HTML filter" after or before the "markdown" filter, when I use them both in the same input format my "empty lines" (as described in the markdown syntax) are not rendered as <p> tags.

I'm using the Aquia Drupal installation right out of the box, with a Zen theme. (for whatever it's worth).

Thanks,
M.M.