# defined somewhere
Listen 80
Listen 443

# in your vhost config
NameVirtualHost *:80
NameVirtualHost *:443

<VirtualHost *:80>
  ServerName domain.com
  # blah blah blah stuff
</VirtualHost>

<VirtualHost *:443>
  ServerName domain.com
  # blah blah blah stuff
  SSLEngine On
  # SSL blah blah blah stuff
</VirtualHost>