The CUSTOM_LEMMY_SERVERS environment variable doesn't appear to work

When I connect to it, I always get lemmy.world as the default instance. Any ideas?

My docker-compose.yml:

services:
  voyager:
    image: ghcr.io/aeharding/voyager:latest
    restart: always
    volumes:
      - "/etc/localtime:/etc/localtime:ro"
    environment:
      - CUSTOM_LEMMY_SERVERS=sh.itjust.works
    labels:
      - com.centurylinklabs.watchtower.enable=true
      - autoheal=true
    healthcheck:
      test: ['CMD-SHELL', 'nc -z localhost 5314 || exit 1']
      interval: 2s
      timeout: 1s
      retries: 10