CI/CD: valid regexp marked as invalid

I have been using the following regexp for several months in my .gitlab-ci.yml and I get suddenly this error for the first time today:

jobs:release docker:except config should be an array of strings or regexps

  stage: release
  only:
    - tags
  except:
    - /^(?!master).+@/
  tags:
    - publish
  before_script:
    - release/checkRelease.sh "$CI_COMMIT_TAG"
  script:
    - sbt publish

The issue seems to come from the look ahead (?).