I'm trying to deploy an IMAP server using docker-compose and secrets for the sensitive data management. I followed the documentation for the long syntax form of creating secrets. But anytime I do docker-compose up -d I get this warning:

WARNING: Service "imap" uses secret "key" with uid, gid, or mode. These fields are not supported by this implementation of the Compose file
WARNING: Service "imap" uses secret "cert" with uid, gid, or mode. These fields are not supported by this implementation of the Compose file

This actually doesn't prevent the containers from being deployed though. But none of the properties set in the docker-compose.yml file are applied to the generated files inside the container.

I have already checked for the compatibility table, but according to it, I should not be getting this warning, since I'm running my containers with the following docker engine and docker-compose versions:

$ docker version:

Client:
Version: 17.06.0-ce
API version: 1.30
Go version: go1.8.3
Git commit: 02c1d87
Built: Fri Jun 23 21:20:04 2017
OS/Arch: linux/amd64

Server:
Version: 17.06.0-ce
API version: 1.30 (minimum version 1.12)
Go version: go1.8.3
Git commit: 02c1d87
Built: Fri Jun 23 21:18:59 2017
OS/Arch: linux/amd64
Experimental: false

$ docker-compose version:

docker-compose version 1.14.0, build c7bdf9e
docker-py version: 2.3.0
CPython version: 2.7.9
OpenSSL version: OpenSSL 1.0.1t 3 May 2016

This is my docker-compose.yml file:

version: '3.1'
services:
    imap:
        image: cyrus
        hostname: cyrus
        volumes:
            - volume1
            - volume2
            - volume3
            - volume4
        secrets:
            - source: key
              target: my.key
              uid: '0'
              gid: '109'
              mode: 0640
            - source: cert
              target: my.crt
              uid: '0'
              gid: '109'
              mode: 0640
        ports:
            - 110:110
            - 143:143
            - 993:993
            - 995:995
            - 4190:4190
        restart: always
        networks:
            - mail
    logger:
        image: gliderlabs/logspout
        hostname: logspout
        volumes:
            - /var/run/docker.sock:/var/run/docker.sock
        networks:
            - mail
        command: syslog://log-server-ip:514
networks:
    mail:
        driver: bridge
secrets:
    key:
        file: ./my.key
    cert:
        file: ./my.crt