Filter url incorrect

I am using the the ajax filters plugin and when you select a filter, the filters disappear. If you refresh the page, they return. This appears to be caused by an incorrect url.

The url upon filtering is similar to mysite.com/shop?filter_veg-type=greens. When refreshing the url becomes mysite.com/shop/?filter_veg-type=greens. Note the missing trailing slash on the page where the filters break. Is there a way to circumvent this to ensure the trailing slash is included so the filters will show after each selection??]