Trigger Gitlab Webhook on Pull Request Merge

In the Webhook configuration trigger section. There is an option to trigger a webhook on merge request events. My question is, I only want to trigger the webhook when the pull request is finally merged. I do not want to trigger the webhook when a merge request is created or updated. However, I am not seeing an option or any granular control to only trigger the webhook on a merge event. Can anyone advise me on if Gitlab supports this and how to trigger a Jenkins build only on a merge event and nothing else? Thanks in advance.