diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index 573b21c2..fda24019 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -51,7 +51,7 @@ const size_t SHRPX_HTTPS_MAX_HEADER_LENGTH = 64*1024;
 HttpsUpstream::HttpsUpstream(ClientHandler *handler)
   : handler_(handler),
     current_header_length_(0),
-    downstream_(0),
+    downstream_(nullptr),
     ioctrl_(handler->get_bev())
 {
   http_parser_init(&htp_, HTTP_REQUEST);
@@ -71,13 +71,12 @@ void HttpsUpstream::reset_current_header_length()
 namespace {
 int htp_msg_begin(http_parser *htp)
 {
-  HttpsUpstream *upstream;
-  upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
+  auto upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
   if(LOG_ENABLED(INFO)) {
     ULOG(INFO, upstream) << "HTTP request started";
   }
   upstream->reset_current_header_length();
-  Downstream *downstream = new Downstream(upstream, 0, 0);
+  auto downstream = new Downstream(upstream, 0, 0);
   upstream->attach_downstream(downstream);
   return 0;
 }
@@ -86,9 +85,8 @@ int htp_msg_begin(http_parser *htp)
 namespace {
 int htp_uricb(http_parser *htp, const char *data, size_t len)
 {
-  HttpsUpstream *upstream;
-  upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
-  Downstream *downstream = upstream->get_downstream();
+  auto upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
+  auto downstream = upstream->get_downstream();
   downstream->append_request_path(data, len);
   return 0;
 }
@@ -97,9 +95,8 @@ int htp_uricb(http_parser *htp, const char *data, size_t len)
 namespace {
 int htp_hdr_keycb(http_parser *htp, const char *data, size_t len)
 {
-  HttpsUpstream *upstream;
-  upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
-  Downstream *downstream = upstream->get_downstream();
+  auto upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
+  auto downstream = upstream->get_downstream();
   if(downstream->get_request_header_key_prev()) {
     downstream->append_last_request_header_key(data, len);
   } else {
@@ -112,9 +109,8 @@ int htp_hdr_keycb(http_parser *htp, const char *data, size_t len)
 namespace {
 int htp_hdr_valcb(http_parser *htp, const char *data, size_t len)
 {
-  HttpsUpstream *upstream;
-  upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
-  Downstream *downstream = upstream->get_downstream();
+  auto upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
+  auto downstream = upstream->get_downstream();
   if(downstream->get_request_header_key_prev()) {
     downstream->set_last_request_header_value(std::string(data, len));
   } else {
@@ -128,12 +124,11 @@ namespace {
 int htp_hdrs_completecb(http_parser *htp)
 {
   int rv;
-  HttpsUpstream *upstream;
-  upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
+  auto upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
   if(LOG_ENABLED(INFO)) {
     ULOG(INFO, upstream) << "HTTP request headers completed";
   }
-  Downstream *downstream = upstream->get_downstream();
+  auto downstream = upstream->get_downstream();
 
   downstream->set_request_method(http_method_str((enum http_method)htp->method));
   downstream->set_request_major(htp->http_major);
@@ -148,7 +143,7 @@ int htp_hdrs_completecb(http_parser *htp)
        << downstream->get_request_path() << " "
        << "HTTP/" << downstream->get_request_major() << "."
        << downstream->get_request_minor() << "\n";
-    const Headers& headers = downstream->get_request_headers();
+    const auto& headers = downstream->get_request_headers();
     for(size_t i = 0; i < headers.size(); ++i) {
       ss << TTY_HTTP_HD << headers[i].first << TTY_RST << ": "
          << headers[i].second << "\n";
@@ -160,7 +155,7 @@ int htp_hdrs_completecb(http_parser *htp)
      downstream->get_request_method() != "CONNECT") {
     // Make sure that request path is an absolute URI.
     http_parser_url u;
-    const char *url = downstream->get_request_path().c_str();
+    auto url = downstream->get_request_path().c_str();
     memset(&u, 0, sizeof(u));
     rv = http_parser_parse_url(url,
                                downstream->get_request_path().size(),
@@ -171,8 +166,7 @@ int htp_hdrs_completecb(http_parser *htp)
     }
   }
 
-  DownstreamConnection *dconn;
-  dconn = upstream->get_client_handler()->get_downstream_connection();
+  auto dconn = upstream->get_client_handler()->get_downstream_connection();
 
   if(downstream->get_expect_100_continue()) {
     static const char reply_100[] = "HTTP/1.1 100 Continue\r\n\r\n";
@@ -205,9 +199,8 @@ namespace {
 int htp_bodycb(http_parser *htp, const char *data, size_t len)
 {
   int rv;
-  HttpsUpstream *upstream;
-  upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
-  Downstream *downstream = upstream->get_downstream();
+  auto upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
+  auto downstream = upstream->get_downstream();
   rv = downstream->push_upload_data_chunk
     (reinterpret_cast<const uint8_t*>(data), len);
   if(rv != 0) {
@@ -221,12 +214,11 @@ namespace {
 int htp_msg_completecb(http_parser *htp)
 {
   int rv;
-  HttpsUpstream *upstream;
-  upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
+  auto upstream = reinterpret_cast<HttpsUpstream*>(htp->data);
   if(LOG_ENABLED(INFO)) {
     ULOG(INFO, upstream) << "HTTP request completed";
   }
-  Downstream *downstream = upstream->get_downstream();
+  auto downstream = upstream->get_downstream();
   downstream->set_request_state(Downstream::MSG_COMPLETE);
   rv = downstream->end_upload_data();
   if(rv != 0) {
@@ -256,10 +248,10 @@ http_parser_settings htp_hooks = {
 // one http request is fully received.
 int HttpsUpstream::on_read()
 {
-  bufferevent *bev = handler_->get_bev();
-  evbuffer *input = bufferevent_get_input(bev);
+  auto bev = handler_->get_bev();
+  auto input = bufferevent_get_input(bev);
   size_t inputlen = evbuffer_get_length(input);
-  unsigned char *mem = evbuffer_pullup(input, -1);
+  auto mem = evbuffer_pullup(input, -1);
 
   if(inputlen == 0) {
     return 0;
@@ -293,7 +285,7 @@ int HttpsUpstream::on_read()
   // execution
   downstream = get_downstream();
   auto handler = get_client_handler();
-  http_errno htperr = HTTP_PARSER_ERRNO(&htp_);
+  auto htperr = HTTP_PARSER_ERRNO(&htp_);
   if(htperr == HPE_PAUSED) {
     if(downstream->get_request_state() == Downstream::CONNECT_FAIL) {
       handler->set_should_close_after_write(true);
@@ -358,7 +350,7 @@ int HttpsUpstream::on_read()
 int HttpsUpstream::on_write()
 {
   int rv = 0;
-  Downstream *downstream = get_downstream();
+  auto downstream = get_downstream();
   if(downstream) {
     rv = downstream->resume_read(SHRPX_NO_BUFFER);
   }
@@ -395,10 +387,9 @@ int HttpsUpstream::resume_read(IOCtrlReason reason, Downstream *downstream)
 namespace {
 void https_downstream_readcb(bufferevent *bev, void *ptr)
 {
-  DownstreamConnection *dconn = reinterpret_cast<DownstreamConnection*>(ptr);
-  Downstream *downstream = dconn->get_downstream();
-  HttpsUpstream *upstream;
-  upstream = static_cast<HttpsUpstream*>(downstream->get_upstream());
+  auto dconn = reinterpret_cast<DownstreamConnection*>(ptr);
+  auto downstream = dconn->get_downstream();
+  auto upstream = static_cast<HttpsUpstream*>(downstream->get_upstream());
   int rv;
   rv = downstream->on_read();
   if(downstream->get_response_state() == Downstream::MSG_RESET) {
@@ -414,7 +405,7 @@ void https_downstream_readcb(bufferevent *bev, void *ptr)
         // Keep-alive
         dconn->detach_downstream(downstream);
       }
-      ClientHandler *handler = upstream->get_client_handler();
+      auto handler = upstream->get_client_handler();
       if(downstream->get_request_state() == Downstream::MSG_COMPLETE) {
         if(handler->get_should_close_after_write() &&
            handler->get_pending_write_length() == 0) {
@@ -449,8 +440,8 @@ void https_downstream_readcb(bufferevent *bev, void *ptr)
         }
       }
     } else {
-      ClientHandler *handler = upstream->get_client_handler();
-      bufferevent *bev = handler->get_bev();
+      auto handler = upstream->get_client_handler();
+      auto bev = handler->get_bev();
       size_t outputlen = evbuffer_get_length(bufferevent_get_output(bev));
       if(outputlen > SHRPX_HTTPS_UPSTREAM_OUTPUT_UPPER_THRES) {
         downstream->pause_read(SHRPX_NO_BUFFER);
@@ -486,10 +477,9 @@ void https_downstream_writecb(bufferevent *bev, void *ptr)
   if(evbuffer_get_length(bufferevent_get_output(bev)) > 0) {
     return;
   }
-  DownstreamConnection *dconn = reinterpret_cast<DownstreamConnection*>(ptr);
-  Downstream *downstream = dconn->get_downstream();
-  HttpsUpstream *upstream;
-  upstream = static_cast<HttpsUpstream*>(downstream->get_upstream());
+  auto dconn = reinterpret_cast<DownstreamConnection*>(ptr);
+  auto downstream = dconn->get_downstream();
+  auto upstream = static_cast<HttpsUpstream*>(downstream->get_upstream());
   // May return -1
   upstream->resume_read(SHRPX_NO_BUFFER, downstream);
 }
@@ -498,10 +488,9 @@ void https_downstream_writecb(bufferevent *bev, void *ptr)
 namespace {
 void https_downstream_eventcb(bufferevent *bev, short events, void *ptr)
 {
-  DownstreamConnection *dconn = reinterpret_cast<DownstreamConnection*>(ptr);
-  Downstream *downstream = dconn->get_downstream();
-  HttpsUpstream *upstream;
-  upstream = static_cast<HttpsUpstream*>(downstream->get_upstream());
+  auto dconn = reinterpret_cast<DownstreamConnection*>(ptr);
+  auto downstream = dconn->get_downstream();
+  auto upstream = static_cast<HttpsUpstream*>(downstream->get_upstream());
   if(events & BEV_EVENT_CONNECTED) {
     if(LOG_ENABLED(INFO)) {
       DCLOG(INFO, dconn) << "Connection established";
@@ -519,7 +508,7 @@ void https_downstream_eventcb(bufferevent *bev, short events, void *ptr)
       upstream->on_downstream_body_complete(downstream);
       downstream->set_response_state(Downstream::MSG_COMPLETE);
 
-      ClientHandler *handler = upstream->get_client_handler();
+      auto handler = upstream->get_client_handler();
       if(handler->get_should_close_after_write() &&
          handler->get_pending_write_length() == 0) {
         // If all upstream response body has already written out to
@@ -578,7 +567,7 @@ void https_downstream_eventcb(bufferevent *bev, short events, void *ptr)
 
 int HttpsUpstream::error_reply(int status_code)
 {
-  std::string html = http::create_error_html(status_code);
+  auto html = http::create_error_html(status_code);
   std::string header;
   header.reserve(512);
   header += "HTTP/1.1 ";
@@ -592,13 +581,13 @@ int HttpsUpstream::error_reply(int status_code)
     header += "Connection: close\r\n";
   }
   header += "\r\n";
-  evbuffer *output = bufferevent_get_output(handler_->get_bev());
+  auto output = bufferevent_get_output(handler_->get_bev());
   if(evbuffer_add(output, header.c_str(), header.size()) != 0 ||
      evbuffer_add(output, html.c_str(), html.size()) != 0) {
     ULOG(FATAL, this) << "evbuffer_add() failed";
     return -1;
   }
-  Downstream *downstream = get_downstream();
+  auto downstream = get_downstream();
   if(downstream) {
     downstream->set_response_state(Downstream::MSG_COMPLETE);
   }
@@ -708,7 +697,7 @@ int HttpsUpstream::on_downstream_header_complete(Downstream *downstream)
     }
     ULOG(INFO, this) << "HTTP response headers\n" << hdrp;
   }
-  evbuffer *output = bufferevent_get_output(handler_->get_bev());
+  auto output = bufferevent_get_output(handler_->get_bev());
   if(evbuffer_add(output, hdrs.c_str(), hdrs.size()) != 0) {
     ULOG(FATAL, this) << "evbuffer_add() failed";
     return -1;
@@ -727,7 +716,7 @@ int HttpsUpstream::on_downstream_body(Downstream *downstream,
   if(len == 0) {
     return 0;
   }
-  evbuffer *output = bufferevent_get_output(handler_->get_bev());
+  auto output = bufferevent_get_output(handler_->get_bev());
   if(downstream->get_chunked_response()) {
     char chunk_size_hex[16];
     rv = snprintf(chunk_size_hex, sizeof(chunk_size_hex), "%X\r\n",
@@ -753,7 +742,7 @@ int HttpsUpstream::on_downstream_body(Downstream *downstream,
 int HttpsUpstream::on_downstream_body_complete(Downstream *downstream)
 {
   if(downstream->get_chunked_response()) {
-    evbuffer *output = bufferevent_get_output(handler_->get_bev());
+    auto output = bufferevent_get_output(handler_->get_bev());
     if(evbuffer_add(output, "0\r\n\r\n", 5) != 0) {
       ULOG(FATAL, this) << "evbuffer_add() failed";
       return -1;
@@ -764,7 +753,7 @@ int HttpsUpstream::on_downstream_body_complete(Downstream *downstream)
   }
   if(downstream->get_request_connection_close() ||
      downstream->get_response_connection_close()) {
-    ClientHandler *handler = get_client_handler();
+    auto handler = get_client_handler();
     handler->set_should_close_after_write(true);
   }
   return 0;