How to prevent links getting automatic http protocol?

I'm using CKEditor to edit templates that contain placeholders for various elements, including URLs. If I have a placeholder tag like '[[my_link]]' and insert it as a link using the link button in the toolbar, it gets inserted as 'http://[[my_link]]' which will break when the tag renders to a full URL. How can I make the link dialog's protocol default to '<other>' instead of http? I don't mind it automatically switching to http if that's what you enter, it's just using as the default that's a problem.