Fast_404 returns true if page starts with an existent path in menu_router

Hi,
Fast_404 returns true if page starts with an existent path in menu_router.
Example: http://xxx.com/adminpagenotfound
in line 147
{
$sql = "SELECT path FROM {menu_router} WHERE ? LIKE CONCAT(path, '%')";
}
is returned "admin", so fast_404 return TRUE.

Thanks