How Do I Remove Site name and Site url from Checkout Page Heading?

I'd like to choose my own title for the checkout page. So I go to Pro Sites settings, , click on edit checkout page and enter a new page title. However when I look at the check out page, the blog name and URL are tagged on to my title.

What I get is something like......
<h1>[My custom site title]: [site name] (site url)</h1>.

All I want is my custom site title. How do I get rid of the appended site name and site url?