Docker: Additional property pull_policy is not allowed – Nginx

Hi guys and excuse me for my English. I’m using docker swarm, when I attempt to deploy docker application with this command

docker stack deploy -c docker-compose.yml -c docker-compose.prod.yml chatappapi

it shows the next error : services.chat-app-api Additional property pull_policy is not allowed

why this happens?
how do I solve this?

docker-compose.yml

version: "3.9"
services:
    nginx:
        image: nginx:stable-alpine 
        ports: 
            - "5000:80"
        volumes:
            - ./nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
    chat-app-api:
        build: .
        image: username/myapp
        pull_policy: always
        volumes:
            - ./:/app
            - /app/node_modules
        environment: 
            - PORT= 5000
            - MAIL_USERNAME=${MAIL_USERNAME}
            - MAIL_PASSWORD=${MAIL_PASSWORD}
            - CLIENT_ID=${CLIENT_ID}
            - CLIENT_SECRET=${CLIENT_SECRET}
            - REDIRECT_URI=${REDIRECT_URI}
            - REFRESH_TOKEN=${REFRESH_TOKEN}
        depends_on: 
            - mongo-db
    mongo-db:
        image: mongo
        environment: 
            MONGO_INITDB_ROOT_USERNAME: 'username'
            MONGO_INITDB_ROOT_PASSWORD: 'password'
        ports:
            - "27017:27017"
        volumes: 
            - mongo-db:/data/db
volumes: 
    mongo-db:

docker-compose.prod.yml

version: "3.9"
services: 
    nginx:
        ports: 
            - "80:80"
    chat-app-api:
        deploy:
            mode: replicated
            replicas: 8
            restart_policy:
                condition: any
            update_config:
                parallelism: 2
                delay: 15s
        build:
            context: .
            args: 
                NODE_ENV: production
        environment: 
            - NODE_ENV=production
            - MONGO_USER=${MONGO_USER}
            - MONGO_PASSWORD=${MONGO_PASSWORD}
            - MONGO_IP=${MONGO_IP}
        command: node index.js
    mongo-db:
        environment: 
            MONGO_INITDB_ROOT_USERNAME: ${MONGO_USER}
            MONGO_INITDB_ROOT_PASSWORD: ${MONGO_PASSWORD}

Information

• docker-compose version 1.29.2
• Docker version 20.10.8
• Ubuntu 20.04.2 LTS

Thanks in advance.