Adding hr-tag to the list of allowed tags produces invalid XHTML

Hi,

I just added "hr" to the list of allowed tags in "Filtered HTML".
After storing the page, Drupal creates code where the hr-tags are contained inside of the paragraph-tags.
This produces invalid XHTML-pages.
What can I do to tell Drupal to put the hr-tag outside of the p-tags?

Thanks in advance!

Peter