Reuse client's port from frontend connection in upstream connection

version 1.8.27 here.

Here’s the connection in question:

client ----1-----> frontend IP
                   haproxy IP    ----2-----> server

I’d like to have the same source port from the connection 1. coming to the frontend (a high port which the client generates) to be used in the 2nd connection, where the haproxy actually connects to the server.
The frontend IP and haproxy IP are different.

What I have tried so far is:

http-request set-src-port


tcp-request connection set-src-port

but it has had no effect - checked via tcpdumps.