WP Twitter over https

I’m using WP Twitter on a website on which I’ve recently set up HTTPS/SSL. But as WP Twitter loads several scripts over http for his integration (http://w.sharethis.com/button/buttons.js, …), I got some message saying that there is unsafe content on some browsers, and some others simply disable the “sharing” buttons.

Is there any way to avoid this, appart from disabling integration and using another plugin for the sharing buttons?

https://wordpress.org/plugins/wp-twitter/