How can I visually test the layout of a page with BackstopJS when there is an A/B-Test running?

I want to test a page with BackstopJS. The problem is, that at the moment there is an A/B test running. So the reference screenshots gets compared with the new test screenshot. But this test screenshot is the other page from the A/B test. I want to use BackstopJS to always test on the same Page for example always on page A from the A/B test. Can somebody help me?