HTTP/2 Server Push from Apache behind HAProxy

I’am wondering if it is possible to use the HTTP/2 Server Push feature behind HAProxy. I have created an simple setup to test it, as far as i can see, the Apache Webserver does not push the content if behind a HAProxy. For testing i have used the nghttp client.

I hope it is ok if i post a link to the same question at serverfault, there i have posted details of my test configuration: https://serverfault.com/questions/1010082/http-2-server-push-from-apache-behind-haproxy

Maybe it is just a fundamental misunderstanding on my part, so far i have found nothing concerning this setup.

Many thanks in advance