diff --git a/src/shrpx-unittest.cc b/src/shrpx-unittest.cc
index da427740..88c1dc40 100644
--- a/src/shrpx-unittest.cc
+++ b/src/shrpx-unittest.cc
@@ -115,6 +115,8 @@ int main(int argc, char *argv[]) {
                    shrpx::test_downstream_assemble_request_cookie) ||
       !CU_add_test(pSuite, "downstream_rewrite_location_response_header",
                    shrpx::test_downstream_rewrite_location_response_header) ||
+      !CU_add_test(pSuite, "downstream_supports_non_final_response",
+                   shrpx::test_downstream_supports_non_final_response) ||
       !CU_add_test(pSuite, "config_parse_header",
                    shrpx::test_shrpx_config_parse_header) ||
       !CU_add_test(pSuite, "config_parse_log_format",
diff --git a/src/shrpx_downstream.cc b/src/shrpx_downstream.cc
index e4236e54..5683dac8 100644
--- a/src/shrpx_downstream.cc
+++ b/src/shrpx_downstream.cc
@@ -743,6 +743,10 @@ bool Downstream::get_non_final_response() const {
   return !upgraded_ && resp_.http_status / 100 == 1;
 }
 
+bool Downstream::supports_non_final_response() const {
+  return req_.http_major == 2 || (req_.http_major == 1 && req_.http_minor == 1);
+}
+
 bool Downstream::get_upgraded() const { return upgraded_; }
 
 bool Downstream::get_http2_upgrade_request() const {
diff --git a/src/shrpx_downstream.h b/src/shrpx_downstream.h
index 28c177d4..42ff4013 100644
--- a/src/shrpx_downstream.h
+++ b/src/shrpx_downstream.h
@@ -348,6 +348,9 @@ public:
   // True if the response is non-final (1xx status code).  Note that
   // if connection was upgraded, 101 status code is treated as final.
   bool get_non_final_response() const;
+  // True if protocol version used by client supports non final
+  // response.  Only HTTP/1.1 and HTTP/2 clients support it.
+  bool supports_non_final_response() const;
   void set_expect_final_response(bool f);
   bool get_expect_final_response() const;
 
diff --git a/src/shrpx_downstream_test.cc b/src/shrpx_downstream_test.cc
index 77895305..fc8c54a8 100644
--- a/src/shrpx_downstream_test.cc
+++ b/src/shrpx_downstream_test.cc
@@ -164,4 +164,29 @@ void test_downstream_rewrite_location_response_header(void) {
   CU_ASSERT("https://localhost:8443/" == (*location).value);
 }
 
+void test_downstream_supports_non_final_response(void) {
+  Downstream d(nullptr, nullptr, 0);
+  auto &req = d.request();
+
+  req.http_major = 2;
+  req.http_minor = 0;
+
+  CU_ASSERT(d.supports_non_final_response());
+
+  req.http_major = 1;
+  req.http_minor = 1;
+
+  CU_ASSERT(d.supports_non_final_response());
+
+  req.http_major = 1;
+  req.http_minor = 0;
+
+  CU_ASSERT(!d.supports_non_final_response());
+
+  req.http_major = 0;
+  req.http_minor = 9;
+
+  CU_ASSERT(!d.supports_non_final_response());
+}
+
 } // namespace shrpx
diff --git a/src/shrpx_downstream_test.h b/src/shrpx_downstream_test.h
index f7b1e603..c042de17 100644
--- a/src/shrpx_downstream_test.h
+++ b/src/shrpx_downstream_test.h
@@ -36,6 +36,7 @@ void test_downstream_field_store_header(void);
 void test_downstream_crumble_request_cookie(void);
 void test_downstream_assemble_request_cookie(void);
 void test_downstream_rewrite_location_response_header(void);
+void test_downstream_supports_non_final_response(void);
 
 } // namespace shrpx
 
diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index 976904ed..ef8c4e56 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -1022,6 +1022,11 @@ int HttpsUpstream::on_downstream_header_complete(Downstream *downstream) {
   auto &resp = downstream->response();
   auto &balloc = downstream->get_block_allocator();
 
+  if (!downstream->supports_non_final_response()) {
+    resp.fs.clear_headers();
+    return 0;
+  }
+
 #ifdef HAVE_MRUBY
   if (!downstream->get_non_final_response()) {
     auto worker = handler_->get_worker();