Hide breadcrumbs on user profiles.

Hey, I'm trying to hide breadcrumbs on user profiles, but the snippet I discovered to do so doesn't seem to work on zen.

function phptemplate_preprocess_page(&$variables) {
  // Disable breadcrumbs only on a user's profile page.
  if (arg(0) == 'user' && is_numeric(arg(1)) && !arg(2)) {
    unset($variables['breadcrumb']);
  }
}

Is what I found. How can i get this to work with zen? I tried switching 'variables' to 'vars' but no luck there.