diff --git a/src/shrpx_downstream.cc b/src/shrpx_downstream.cc
index 87e8ff58..60428783 100644
--- a/src/shrpx_downstream.cc
+++ b/src/shrpx_downstream.cc
@@ -1211,4 +1211,8 @@ void Downstream::detach_blocked_link(BlockedLink *l) {
   blocked_link_ = nullptr;
 }
 
+void Downstream::add_request_headers_sum(size_t amount) {
+  request_headers_sum_ += amount;
+}
+
 } // namespace shrpx
diff --git a/src/shrpx_downstream.h b/src/shrpx_downstream.h
index 0388adea..f761b6a0 100644
--- a/src/shrpx_downstream.h
+++ b/src/shrpx_downstream.h
@@ -143,6 +143,7 @@ public:
   void set_request_method(std::string method);
   const std::string &get_request_method() const;
   void set_request_path(std::string path);
+  void add_request_headers_sum(size_t amount);
   void
   set_request_start_time(std::chrono::high_resolution_clock::time_point time);
   const std::chrono::high_resolution_clock::time_point &
diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index b3f1a029..e620a5da 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -78,6 +78,17 @@ namespace {
 int htp_uricb(http_parser *htp, const char *data, size_t len) {
   auto upstream = static_cast<HttpsUpstream *>(htp->data);
   auto downstream = upstream->get_downstream();
+  if (downstream->get_request_headers_sum() + len >
+      get_config()->header_field_buffer) {
+    if (LOG_ENABLED(INFO)) {
+      ULOG(INFO, upstream) << "Too large URI size="
+                           << downstream->get_request_headers_sum() + len;
+    }
+    assert(downstream->get_request_state() == Downstream::INITIAL);
+    downstream->set_request_state(Downstream::HTTP1_REQUEST_HEADER_TOO_LARGE);
+    return -1;
+  }
+  downstream->add_request_headers_sum(len);
   downstream->append_request_path(data, len);
   return 0;
 }