Change primary domain from HTTP to HTTPS

I have added an SSL Certificate to my multisite and have been able to update all the sub-directory sites to HTTPS, installed the “WordPress HTTPS” plugin and forced SSL on the entire site, however, there is no option to edit the primary domain from HTTP to HTTPS.

How can I change the primary domain to HTTPS?

It would be handy if WordPress allowed the HTTP on multisites to be easily editable (just as it is on a single site) for those changing to HTTPS.