HSTS on Port 80 on SSL Redirect

Hey Traefik community,

we are using Traefik as a LoadBalancer in some customer project. The customer is using an external security scan provider to check their website for security vulnabilities. This scan gives out an error for port 80 which requests to set the HSTS header also for port 80 (it is correctly send on port 443).
We have a SSL redirect set up on the LoadBalancer using a middleware:

apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
  name: stsheaders
  namespace: default
spec:
  headers:
    browserXssFilter: true
    contentTypeNosniff: true
    customFrameOptionsValue: SAMEORIGIN
    forceSTSHeader: true
    frameDeny: true
    sslRedirect: true
    stsIncludeSubdomains: true
    stsPreload: true
    stsSeconds: 31536000

We have set forceSTSHeader to true, however the response is giving the 301 like it should, but not the HSTS header.

curl -v http://my-app.com
*   Trying 1.2.3.4:80...
* Connected to my-app.com (1.2.4.5) port 80 (#0)
> GET / HTTP/1.1
> Host: my-app.com
> User-Agent: curl/7.77.0
> Accept: */*
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 301 Moved Permanently
< Content-Type: text/html; charset=utf-8
< Location: https://my-app.com/
< Date: Tue, 18 Jan 2022 14:27:44 GMT
< Content-Length: 56
<
<a href="https://my-app.com/">Moved Permanently</a>.


* Connection #0 to host my-app.com left intact

I hope someone can help.

Greetings Sven