On top of what @baris said, if you are using a reverse-proxy like nginx, you can add that location to redirect to the same place.
Every now and again one of my users informs me that he is getting a forbidden message after trying to register. I have tried to replicate this on phones, tablets, different browsers and I never have a problem signing up to my forum.
Has anybody got a clue as to what might be happening every once in a while to people trying to sign up?
Running v1.7.0 on CENTOS 7 with NGINX reverse proxy.