How to exclude the master branch from the GitLab 13 ci build process?

I want the build process to run for all branches when I add a tag. Except for the master branch.

deploy_qas:
  stage: deploy
  script:
   - echo "Implatado em QAS"
  environment:
    name: qas
    url: https://env.br
  only:
  - tags
  except:
  - master

This way it is not working.

I am using GitLab 13 ce.