Redirect back goes to wrong page

I have a Ruby on Rails app and whenever I click on a button in it that submits a POST request, instead of redirecting back, it sends me to a GET of the POST request. For example I am at /a, I make a POST request to /a/b, instead of redirecting back to /a, it sends me to /a/b which returns a 404 as there is only a POST defined at this route. I have tested this same site in Chromium and the redirects work properly, returning me back to /a