Configuring custom error pages in traefik1

Hi all,
I'm facing an issue when trying to setup error pages on traefik1. This is what we're trying to implement:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
    external-dns.alpha.kubernetes.io/hostname: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.
    external-dns.alpha.kubernetes.io/ttl: "300"
    ingress.kubernetes.io/custom-response-headers: Server:Traefik
    kubernetes.io/ingress.class: traefik
    traefik.ingress.kubernetes.io/error-pages: |
      notfound:
        status:
        - "404"
        backend: nginx-error-service
        query: "/jenkins_404.html"
      error:
        status:
        - "500"
        backend: nginx-error-service
        query: "/jenkins_500.html"
      maintenance:
        status:
        - "502"
        - "503"
        - "504"
        backend: nginx-error-service
        query: "/jenkins_502.html"
    traefik.ingress.kubernetes.io/frontend-entry-points: http,https
    traefik.ingress.kubernetes.io/redirect-entry-point: https
    traefik.ingress.kubernetes.io/redirect-permanent: "true"
  labels:
    io.cattle.field/appId: devops-jenkins
  name: devops-jenkins-jenkins-dsu
  namespace: devops-jenkins
  spec:
  rules:
  - host: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    http:
      paths:
      - backend:
          serviceName: devops-jenkins-jenkins-dsu
          servicePort: 8080

We're getting this error:

time="2020-01-10T16:39:04Z" level=error msg="Error when creating error page \"error\" for frontend \"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx": the backend \"nginx-error-service\" doesn't exist."
time="2020-01-10T16:39:04Z" level=error msg="Error when creating error page \"maintenance\" for frontend \"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx": the backend \"nginx-error-service\" doesn't exist."
time="2020-01-10T16:39:04Z" level=error msg="Error when creating error page \"notfound\" for frontend \"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx": the backend \"nginx-error-service\" doesn't exist."

The service exists:

❯ k get services -n kube-system nginx-error-service -o yaml
apiVersion: v1
kind: Service
metadata:
  annotations:
    kubernetes.io/ingress.class: traefik
  labels:
    Toolkit: Shared
  name: nginx-error-service
  namespace: kube-system
  ports:
  - name: http
    port: 80
    protocol: TCP
    targetPort: 80
  selector:
    k8s-app: nginx-error-deployment
  type: ClusterIP

To which resource the ingress controller is trying to reach? It says can't find the backend... i'm i wrong to point the "backend" to a service??

Thanks in advance!