How to share artifacts in cross project pipeline

I use a cross project pipeline to publish a Helm chart using GitLab pages.

I have the following GitLab CI job in appsemble/appsemble:

publish helm:
  needs:
    - helm package
  stage: publish
  variables:
    PARENT_PIPELINE_ID: $CI_PIPELINE_ID
    VERSION: $CI_COMMIT_TAG
  rules:
    - if: $CI_COMMIT_TAG
  trigger:
    project: appsemble/charts
    strategy: depend

The helm package job runs fine.

This triggers the following pipeline in appsemble/charts:

stages:
  - test
  - build
  - deploy

git:
  image: alpine
  stage: build
  rules:
    - if: $PARENT_PIPELINE_ID
  needs:
    - pipeline: $PARENT_PIPELINE_ID
      job: helm package
      artifacts: true
  script:
    - apk add git gnupg
    - gpg --import "$GPG_PRIVATE_KEY"
    - git config commit.gpgSign true
    - git config user.email bot@appsemble.com
    - git config user.name Appsemble
    - git add .
    - git commit --message "Add Appsemble Helm chart $VERSION"
    - git push origin main --push-option ci.skip

pages:
  image: dtzar/helm-kubectl:3
  stage: build
  rules:
    - if: $CI_COMMIT_BRANCH == 'main'
  script:
    - helm repo index public
  artifacts:
    paths:
      - public

The CI output can be seen here. The git job output shows:

image

I also tried adding project: appsemble/appsemble to the needs section, but that make GitLab CI lint fail with the following message:

jobs:git:needs:need config contains unknown keys: pipeline
jobs:git:needs:need ref should be a string
jobs:git:needs:need ref can't be blank

How do I fix this, so I the downstream CI job in appsemble/charts uses the job artifacts of an earlier stage in its parent pipeline in appsemble/appsemble?