How to tell Traefik 2.1 to use a user-defined wildcard certificate for a router?

I'm trying to get Traefik to use a manually configured wildcard certificate for all routers that have a matching Host rule. I assumed Traefik would try to find a certificate based on the domains used in the Host rule, but it always uses the default generated certificate instead.

traefik.yml

global:
  checkNewVersion: false
  sendAnonymousUsage: false

log:
  level: DEBUG

entryPoints:
  web:
    address: ":80"
  web-secure:
    address: ":443"

providers:
  file:
    directory: /etc/traefik/conf
    watch: true

dynamic conf:

http:
  routers:
    test:
      rule: "Host(`subdomain.wildcard.domain.tld`)"
      entryPoints: ["web"]
      service: service-test
      middlewares: ["https_redirect"]
    test-secure:
      rule: "Host(`subdomain.wildcard.domain.tld`)"
      entryPoints: ["web-secure"]
      service: service-test
      tls: {}

  services:
    service-test:
      loadBalancer:
        servers:
          - url: "http://helloworld"

  middlewares:
    https_redirect:
      redirectScheme:
        scheme: https
        permanent: true

Traefik is running inside a Docker container, based on the log it can see and use the mounted certificate files:

time="2020-03-04T10:44:13Z" level=debug msg="No store is defined to add the certificate <...>, it will be added to the default store."
time="2020-03-04T10:44:13Z" level=debug msg="Adding certificate for domain(s) wildcard.domain.tld,*.wildcard.domain.tld"
time="2020-03-04T10:44:13Z" level=debug msg="No default certificate, generating one"

However, when doing a curl request, the default certificate is used:

curl -k -v --header "Host: subdomain.wildcard.domain.tld" https://192.168.173.143/

* Server certificate:
*  subject: CN=TRAEFIK DEFAULT CERT
*  start date: Mar  4 10:44:13 2020 GMT
*  expire date: Mar  4 10:44:13 2021 GMT
*  issuer: CN=TRAEFIK DEFAULT CERT
*  SSL certificate verify result: unable to get local issuer certificate (20), continuing anyway.

When specifyng the certificate as the default certificate, Traefik does use it, making it more obvious that something is wrong when it tries to match the routers to fitting certificates.

tls:
  certificates:
    - certFile: /ssl/wildcard.crt
      keyFile: /ssl/wildcard.key
  stores:
    default:
      defaultCertificate:
        certFile: /ssl/wildcard.crt
        keyFile: /ssl/wildcard.key