anchor.diff:      // Via header
   
       if (includeViaHeaderInResponse) {
  -      /// A "Via" header is optional in forwarded responses according to
  -      /// [RFC 7230](https://tools.ietf.org/html/rfc7230#section-5.7.1).
  -
  -      final _newVia = (targetResponse.headers['via'] != null)
  -          ? '${targetResponse.headers['via']}, $_via'
  -          : _via;
  -
  -      resp.headerAdd('via', _newVia);
  -      _logProxyResponse.finest('[${req.id}] + via=$_newVia');
  +      // Add a Via header to the HTTP response.
  +      //
  +      // A "Via" header is optional in forwarded responses according to
  +      // [RFC 7230](https://tools.ietf.org/html/rfc7230#section-5.7.1).
  +      //
  +      // Important: this must be done _after_ copying the headers from the
  +      // proxy response, since this new "Via" header must appear _after_ any
  +      // previous ones.
  +
  +      resp.headerAdd('via', _via);
  +      _logProxyResponse.finest('[${req.id}] + via=$_via');
       }
   
       // Create a stream from the bodyBytes, and use it for the response
  
positive.code: 
      _logProxyResponse.finest('[${req.id}] + content-type=$contentType');
  
      // Identify any connection headers that must not be passed through
  
      // ignore: prefer_collection_literals
      final responseConnectionExclude = Set<String>();
  
negative.code:     passHeaders['host'] = _newHost;
      _logProxyRequest.finest('[${req.id}] + host=$_newHost');
  
      // Identify any link-only headers that must not be passed through.
      // These are identified in the "Connection" header, if any.
  
      // ignore: prefer_collection_literals
      final requestConnectionExclude = Set<String>();
  