Headers sent as lowercase even if specifying http1_title_case_headers()

[GTP95]

Greetings,
I have a class that creates an HTTP client and uses it to do two HTTP requests. Here's how I build the client:

let client_builder = reqwest::Client::builder()
            .connection_verbose(true) //print verbose connection info for debugging
            .redirect(redirect::Policy::none())//Do not follow redirects, so that I can get the code without contacting localhost:16515/
            .http1_title_case_headers();    //case-sensitive headers. See https://github.com/seanmonstar/reqwest/discussions/1895#discussioncomment-6355126
let client = client_builder.build().expect("Error building HTTPS client");

Here's how I build the first request:

let request = self.client
            .get(auth_endpoint_url_with_params)
            .header("Shib-Spoof-Check", &self.spoof_check_secret)
            .header(self.uid_field_name.clone(), uid)
            .body("");

This is the first RequestBuilder serialized:

RequestBuilder { method: GET, url: Url { scheme: "http", cannot_be_a_base: false, username: "", password: None, host: Some(Domain("localhost")), port: Some(8080), path: "/auth", query: Some("&user=participant:bab472a1-f8b7-4397-8338-fb972e3b8280&client_id=123&redirect_uri=http://127.0.0.1:16515/&response_type=code&code_challenge=Yzc4YzUyOTE0NjM3M2E3Y2VjMmY0ZjUwMTE1MDMyYWE5MjQ1MWM1M2IxYmQ3ZGY4MTcxOWFiNzM4NTYxOTUyNA&code_challenge_method=S256"), fragment: None }, headers: {"shib-spoof-check": "be67c8dd6a141ded148861ac11aef64d68640876601a40dca01816004e4c5161", "uid": "participant:bab472a1-f8b7-4397-8338-fb972e3b8280"} }

This is the second request:

let request = self.client.post(token_endpoint)
            .header("Shib-Spoof-Check", &self.spoof_check_secret)
            .header(self.uid_field_name.clone(), uid)
            .json(&request_body);

And its serialization:

RequestBuilder { method: POST, url: Url { scheme: "http", cannot_be_a_base: false, username: "", password: None, host: Some(Domain("localhost")), port: Some(8080), path: "/token", query: None, fragment: None }, headers: {"shib-spoof-check": "be67c8dd6a141ded148861ac11aef64d68640876601a40dca01816004e4c5161", "uid": "participant:bab472a1-f8b7-4397-8338-fb972e3b8280", "content-type": "application/json"} }

Note that in both cases, the "Shib-Spoof-Check" header is sent as lowercase, despite when I constructed the HTTP client I called http1_title_case_headers(). What am I getting wrong?

PS: I'm using reqwest 0.11.20, cargo on my machine isn't able to find version 0.11.22 which seems to be the latest one.

[seanmonstar]

The Debug output of request does not convert the case. The case is handled when written to the socket

[GTP95]

You're right, I double-checked with Wireshark and the headers are capitalized with title-case. Thank you.