Why Alamofire GET 'If-None-Match' does not work?

Question

For example i have the following code:

let headers = ["If-None-Match": etag, "Authorization": "Token token=\(apiKey)"]

Alamofire.request(.GET, "\(AppSettings.ApiURL)/v1/users/", headers: headers).responseJSON { response in

    guard let statusCode = response.response?.statusCode else {return}
    print("status code: \(statusCode)")
}

And i get the status code: 200 every time, instead of 304. The same request with curl or postman is returned 304 status code. I don't know where is mistake. Any help is massively appreciated!