Haproxy 1.7.9 or earlier stopped using h2 (no replies)

Dear all,

I configured some time ago haproxy to support http2 using tcp mode on
FreeBSD.

The configuration looked like:

frontend www-https
    mode tcp
    option tcplog
    bind <ip>:<port> ssl crt /usr/local/etc/haproxy/certs/ alpn h2,http/1.1
    use_backend nginx-http2-backend if { ssl_fc_alpn -i h2 }
    default_backend nginx-http-backend

backend nginx-http2-backend
    mode tcp
    server www-1 127.0.0.1:8083 check send-proxy


Nginx on port 8083 is listing with this line:
listen 127.0.0.1:8083 http2 proxy_protocol;


That worked in the past. I have no idea when it stopped, but currently
it is not working anymore.
Is anyone aware of a change that could cause h2 to not working anymore?

Thanks

Matthias