Create a new virtual host using the same subdomain but listening on port 80.
Here's an example for a default virtualhost (key being the number of the port in the first line of the configuration file) :
<VirtualHost *:80>
ServerName admin.domain.fr
DocumentRoot /var/www
<Directory /var/www/>
Options FollowSymLinks MultiViews
AllowOverride All
Order allow,deny
allow from all
</Directory>
ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
<Directory "/usr/lib/cgi-bin">
AllowOverride None
Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
Order allow,deny
Allow from all
</Directory>
ErrorLog ${APACHE_LOG_DIR}/error.log
# Possible values include: debug, info, notice, warn, error, crit,
# alert, emerg.
LogLevel warn
CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>
You'd have to adapt it to your context of course, notably the document root and the server name.