Gitlab Prefixes web hooks with /project. Breaks Jenkins

I’ve started using folders in Jenkins. One of my jobs is at the URL:

I’m also trying to use Gitlab to post a web hook on commit to the job.

On the Gitlab project page, the Jenkins URL js:

The Project Name is:

When I check the nginx logs (nginx is sitting in front of Jenkins to do SSL termination), I see this:
POST /project/job/Chef%20Cookbooks/job/slice-ntp/job/Jobs/job/chef-cookbook-slice-ntp-build/

So, gitlab is prefixing /project to the front of the URL. If I remove the /project prefix, it works fine. Why is Gitlab doing this and how do I get rid of it? It works fine with jobs not in folders.