aws apprunner env variables in building phase are not visibile

I've this config file

version: 1.0
runtime: nodejs18

build:
  commands:
    pre-build:
      - npm install
    build:
      - npm run build
    post-build:
      - npm test
  env:
    - name: AWS_COGNITO_REGION
      value: "xx-zzzz-x"
    - name: AWS_COGNITO_USERPOOLID
      value: "xx-zzzz-y_yyyyyy"
.........

Both of env variables are needed during the post-build step but I got several errors because

env-var: "AWS_COGNITO_REGION" is a required variable, but it was not set

I've been struggling with this issue for days without any solution. Any suggestion? Could you help me?