getting the correct default gravatar to show…

Hey all,

I have this in comments.php:

<?php echo get_avatar( $comment, $size = '30' ); ?>

It works fine, only it doesn’t show the correct default gravatar for folks who haven’t registered at gravatar.com

ie. in Settings > Discussion I specified “mystery man” as the default, but in the comments it displays the blug G avatar instead.

Any ideas why?

Thank you,