Traefik won't forward to backend configured with Docker labels

Here's my Traefik configuration:

defaultEntryPoints = ["http", "https"]

[entryPoints]
    [entryPoints.http]
    address = ":80"
        [entryPoints.http.redirect]
        entryPoint = "https"

    [entryPoints.https]
    address = ":443"
    [entryPoints.https.tls]

    [entryPoints.internal]
    address = ":8080"

    [entryPoints.traefik]
    address = ":8081"

[retry]

[api]
entryPoint = "traefik"
dashboard = true

[file]
    [backends]
        [backends.traefik]
            [backends.traefik.servers.default]
            url = "http://127.0.0.1:8081"

    [frontends]
        [frontends.traefik]
        entryPoints = ["internal"]
        backend = "traefik"
            [frontends.traefik.routes.default]
            rule = "Host:localhost;PathPrefixStrip:/traefik;PathPrefix:/traefik"

[docker]
domain = "example.com"
watch = true
exposedbydefault = false

As you can see, I have Traefik dashboard configured to show on localhost:8080/traefik. This works exactly as intended.

I also have very similar configuration for RabbitMQ management UI, set up with docker-compose using labels:

version: '3'
services:
  traefik:
    image: traefik:alpine
    container_name: traefik
    ports:
      - "80:80"
      - "443:443"
      - "127.0.0.1:8080:8080"
    networks:
      - web
      - internal
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"
      - "./config/traefik/staging.toml:/etc/traefik/traefik.toml"
  rabbitmq:
    image: rabbitmq:3.7-management-alpine
    hostname: rabbitmq
    container_name: rabbitmq
    networks:
      - internal
      - default
    depends_on:
      - traefik
    environment:
      RABBITMQ_VM_MEMORY_HIGH_WATERMARK: 128MiB
      RABBITMQ_ERLANG_COOKIE: temp_cookie_secret
      RABBITMQ_NODENAME: rabbit@rabbitmq
    volumes:
      - "rabbitmqdata:/var/lib/rabbitmq"
    labels:
      - "traefik.backend=rabbitmq"
      - "traefik.docker.network=internal"
      - "traefik.frontend.rule=Host:localhost;PathPrefixStrip:/rabbitmq;PathPrefix:/rabbitmq"
      - "traefik.enable=true"
      - "traefik.port=15672"
      - "traefik.protocol=http"
      - "traefik.domain=localhost"
networks:
  internal:
  web:
volumes:
  rabbitmqdata

However, this doesn't work: on http://localhost:8080/rabbitmq I get 404 page not found. Traefik dashboard shows that it found my RabbitMQ container and registered rules that are very much like those for Traefik's dashboard:

Traefik dashboard rules RabbitMQ management UI rules

Where's the mistake here that prevents my setup from working as intended?