diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index 24193327..8db78a4b 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -450,19 +450,20 @@ int Http2Handler::submit_response
 {
   std::string date_str = util::http_date(time(0));
   const size_t static_size = 6;
-  auto nv = util::make_unique<const char*[]>(static_size+headers.size()*2+1);
-  nv[0] = ":status";
-  nv[1] = status.c_str();
-  nv[2] = "server";
-  nv[3] = NGHTTPD_SERVER.c_str();
-  nv[4] = "date";
-  nv[5] = date_str.c_str();
-  for(int i = 0; i < (int)headers.size(); ++i) {
-    nv[static_size+i*2] = headers[i].first.c_str();
-    nv[static_size+i*2+1] = headers[i].second.c_str();
+  auto nv = std::vector<const char*>();
+  nv.reserve(static_size + headers.size() * 2 + 1);
+  nv.push_back(":status");
+  nv.push_back(status.c_str());
+  nv.push_back("server");
+  nv.push_back(NGHTTPD_SERVER.c_str());
+  nv.push_back("date");
+  nv.push_back(date_str.c_str());
+  for(size_t i = 0; i < headers.size(); ++i) {
+    nv.push_back(headers[i].first.c_str());
+    nv.push_back(headers[i].second.c_str());
   }
-  nv[static_size+headers.size()*2] = nullptr;
-  int r = nghttp2_submit_response(session_, stream_id, nv.get(), data_prd);
+  nv.push_back(nullptr);
+  int r = nghttp2_submit_response(session_, stream_id, nv.data(), data_prd);
   return r;
 }
 
diff --git a/src/http2.cc b/src/http2.cc
index 343a208c..68e39de8 100644
--- a/src/http2.cc
+++ b/src/http2.cc
@@ -269,16 +269,16 @@ bool value_lws(const nghttp2_nv *nv)
   return true;
 }
 
-size_t copy_norm_headers_to_nv
-(const char **nv,
+void copy_norm_headers_to_nv
+(std::vector<const char*>& nv,
  const std::vector<std::pair<std::string, std::string>>& headers)
 {
-  size_t i, j, nvlen = 0;
+  size_t i, j;
   for(i = 0, j = 0; i < headers.size() && j < IGN_HDLEN;) {
     int rv = strcmp(headers[i].first.c_str(), IGN_HD[j]);
     if(rv < 0) {
-      nv[nvlen++] = headers[i].first.c_str();
-      nv[nvlen++] = headers[i].second.c_str();
+      nv.push_back(headers[i].first.c_str());
+      nv.push_back(headers[i].second.c_str());
       ++i;
     } else if(rv > 0) {
       ++j;
@@ -287,10 +287,9 @@ size_t copy_norm_headers_to_nv
     }
   }
   for(; i < headers.size(); ++i) {
-    nv[nvlen++] = headers[i].first.c_str();
-    nv[nvlen++] = headers[i].second.c_str();
+    nv.push_back(headers[i].first.c_str());
+    nv.push_back(headers[i].second.c_str());
   }
-  return nvlen;
 }
 
 void build_http1_headers_from_norm_headers
diff --git a/src/http2.h b/src/http2.h
index 2583ec0b..0270e7c7 100644
--- a/src/http2.h
+++ b/src/http2.h
@@ -89,11 +89,11 @@ std::string value_to_str(const nghttp2_nv *nv);
 // Returns true if the value of |nv| includes only ' ' (0x20) or '\t'.
 bool value_lws(const nghttp2_nv *nv);
 
-// Copies headers in |headers| to |nv|. Certain headers, including
+// Appends headers in |headers| to |nv|. Certain headers, including
 // disallowed headers in HTTP/2.0 spec and headers which require
 // special handling (i.e. via), are not copied.
-size_t copy_norm_headers_to_nv
-(const char **nv,
+void copy_norm_headers_to_nv
+(std::vector<const char*>& nv,
  const std::vector<std::pair<std::string, std::string>>& headers);
 
 // Appends HTTP/1.1 style header lines to |hdrs| from headers in
diff --git a/src/http2_test.cc b/src/http2_test.cc
index 3f24d950..bd1f7c20 100644
--- a/src/http2_test.cc
+++ b/src/http2_test.cc
@@ -132,9 +132,9 @@ auto headers = std::vector<std::pair<std::string, std::string>>
 
 void test_http2_copy_norm_headers_to_nv(void)
 {
-  const char* nv[30];
-  size_t nvlen = http2::copy_norm_headers_to_nv(nv, headers);
-  CU_ASSERT(12 == nvlen);
+  std::vector<const char*> nv;
+  http2::copy_norm_headers_to_nv(nv, headers);
+  CU_ASSERT(12 == nv.size());
   CU_ASSERT(strcmp(nv[0], "alpha") == 0);
   CU_ASSERT(strcmp(nv[1], "0") == 0);
   CU_ASSERT(strcmp(nv[2], "bravo") == 0);
diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index f03afc14..7be268a3 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -863,20 +863,19 @@ int Http2Upstream::on_downstream_header_complete(Downstream *downstream)
   auto end_headers = std::end(downstream->get_response_headers());
   size_t nheader = downstream->get_response_headers().size();
   // 4 means :status and possible via header field.
-  auto nv = util::make_unique<const char*[]>(nheader * 2 + 4 + 1);
-  size_t hdidx = 0;
+  auto nv = std::vector<const char*>();
+  nv.reserve(nheader * 2 + 4 + 1);
   std::string via_value;
   auto response_status = util::utos(downstream->get_response_http_status());
-  nv[hdidx++] = ":status";
-  nv[hdidx++] = response_status.c_str();
+  nv.push_back(":status");
+  nv.push_back(response_status.c_str());
 
-  hdidx += http2::copy_norm_headers_to_nv(&nv[hdidx],
-                                          downstream->get_response_headers());
+  http2::copy_norm_headers_to_nv(nv, downstream->get_response_headers());
   auto via = downstream->get_norm_response_header("via");
   if(get_config()->no_via) {
     if(via != end_headers) {
-      nv[hdidx++] = "via";
-      nv[hdidx++] = (*via).second.c_str();
+      nv.push_back("via");
+      nv.push_back((*via).second.c_str());
     }
   } else {
     if(via != end_headers) {
@@ -885,10 +884,10 @@ int Http2Upstream::on_downstream_header_complete(Downstream *downstream)
     }
     via_value += http::create_via_header_value
       (downstream->get_response_major(), downstream->get_response_minor());
-    nv[hdidx++] = "via";
-    nv[hdidx++] = via_value.c_str();
+    nv.push_back("via");
+    nv.push_back(via_value.c_str());
   }
-  nv[hdidx++] = nullptr;
+  nv.push_back(nullptr);
   if(LOG_ENABLED(INFO)) {
     std::stringstream ss;
     for(size_t i = 0; nv[i]; i += 2) {
@@ -903,8 +902,8 @@ int Http2Upstream::on_downstream_header_complete(Downstream *downstream)
   data_prd.read_callback = spdy_data_read_callback;
 
   int rv;
-  rv = nghttp2_submit_response(session_, downstream->get_stream_id(), nv.get(),
-                               &data_prd);
+  rv = nghttp2_submit_response(session_, downstream->get_stream_id(),
+                               nv.data(), &data_prd);
   if(rv != 0) {
     ULOG(FATAL, this) << "nghttp2_submit_response() failed";
     return -1;
diff --git a/src/shrpx_spdy_downstream_connection.cc b/src/shrpx_spdy_downstream_connection.cc
index 527a4d96..bdc01c64 100644
--- a/src/shrpx_spdy_downstream_connection.cc
+++ b/src/shrpx_spdy_downstream_connection.cc
@@ -236,15 +236,15 @@ int SpdyDownstreamConnection::push_request_headers()
   // 10 means :method, :scheme, :path and possible via and
   // x-forwarded-for header fields. We rename host header field as
   // :host.
-  auto nv = util::make_unique<const char*[]>(nheader * 2 + 10 + 1);
-  size_t hdidx = 0;
+  auto nv = std::vector<const char*>();
+  nv.reserve(nheader * 2 + 10 + 1);
   std::string via_value;
   std::string xff_value;
   std::string scheme, path, query;
   if(downstream_->get_request_method() == "CONNECT") {
     // No :scheme header field for CONNECT method.
-    nv[hdidx++] = ":path";
-    nv[hdidx++] = downstream_->get_request_path().c_str();
+    nv.push_back(":path");
+    nv.push_back(downstream_->get_request_path().c_str());
   } else {
     http_parser_url u;
     const char *url = downstream_->get_request_path().c_str();
@@ -264,27 +264,26 @@ int SpdyDownstreamConnection::push_request_headers()
         path += query;
       }
     }
-    nv[hdidx++] = ":scheme";
+    nv.push_back(":scheme");
     if(scheme.empty()) {
       // The default scheme is http. For SPDY upstream, the path must
       // be absolute URI, so scheme should be provided.
-      nv[hdidx++] = "http";
+      nv.push_back("http");
     } else {
-      nv[hdidx++] = scheme.c_str();
+      nv.push_back(scheme.c_str());
     }
-    nv[hdidx++] = ":path";
+    nv.push_back(":path");
     if(path.empty()) {
-      nv[hdidx++] = downstream_->get_request_path().c_str();
+      nv.push_back(downstream_->get_request_path().c_str());
     } else {
-      nv[hdidx++] = path.c_str();
+      nv.push_back(path.c_str());
     }
   }
 
-  nv[hdidx++] = ":method";
-  nv[hdidx++] = downstream_->get_request_method().c_str();
+  nv.push_back(":method");
+  nv.push_back(downstream_->get_request_method().c_str());
 
-  hdidx += http2::copy_norm_headers_to_nv(&nv[hdidx],
-                                          downstream_->get_request_headers());
+  http2::copy_norm_headers_to_nv(nv, downstream_->get_request_headers());
 
   auto host = downstream_->get_norm_request_header("host");
   if(host == end_headers) {
@@ -293,8 +292,8 @@ int SpdyDownstreamConnection::push_request_headers()
     }
     return -1;
   }
-  nv[hdidx++] = ":host";
-  nv[hdidx++] = (*host).second.c_str();
+  nv.push_back(":host");
+  nv.push_back((*host).second.c_str());
 
   bool content_length = false;
   if(downstream_->get_norm_request_header("content-length") != end_headers) {
@@ -304,8 +303,8 @@ int SpdyDownstreamConnection::push_request_headers()
   auto expect = downstream_->get_norm_request_header("expect");
   if(expect != end_headers &&
      !util::strifind((*expect).second.c_str(), "100-continue")) {
-    nv[hdidx++] = "expect";
-    nv[hdidx++] = (*expect).second.c_str();
+    nv.push_back("expect");
+    nv.push_back((*expect).second.c_str());
   }
 
   bool chunked_encoding = false;
@@ -318,24 +317,24 @@ int SpdyDownstreamConnection::push_request_headers()
 
   auto xff = downstream_->get_norm_request_header("x-forwarded-for");
   if(get_config()->add_x_forwarded_for) {
-    nv[hdidx++] = "x-forwarded-for";
+    nv.push_back("x-forwarded-for");
     if(xff != end_headers) {
       xff_value = (*xff).second;
       xff_value += ", ";
     }
     xff_value += downstream_->get_upstream()->get_client_handler()->
       get_ipaddr();
-    nv[hdidx++] = xff_value.c_str();
+    nv.push_back(xff_value.c_str());
   } else if(xff != end_headers) {
-    nv[hdidx++] = "x-forwarded-for";
-    nv[hdidx++] = (*xff).second.c_str();
+    nv.push_back("x-forwarded-for");
+    nv.push_back((*xff).second.c_str());
   }
 
   auto via = downstream_->get_norm_request_header("via");
   if(get_config()->no_via) {
     if(via != end_headers) {
-      nv[hdidx++] = "via";
-      nv[hdidx++] = (*via).second.c_str();
+      nv.push_back("via");
+      nv.push_back((*via).second.c_str());
     }
   } else {
     if(via != end_headers) {
@@ -344,10 +343,10 @@ int SpdyDownstreamConnection::push_request_headers()
     }
     via_value += http::create_via_header_value
       (downstream_->get_request_major(), downstream_->get_request_minor());
-    nv[hdidx++] = "via";
-    nv[hdidx++] = via_value.c_str();
+    nv.push_back("via");
+    nv.push_back(via_value.c_str());
   }
-  nv[hdidx++] = nullptr;
+  nv.push_back(nullptr);
 
   if(LOG_ENABLED(INFO)) {
     std::stringstream ss;
@@ -363,9 +362,9 @@ int SpdyDownstreamConnection::push_request_headers()
     nghttp2_data_provider data_prd;
     data_prd.source.ptr = this;
     data_prd.read_callback = spdy_data_read_callback;
-    rv = spdy_->submit_request(this, 0, nv.get(), &data_prd);
+    rv = spdy_->submit_request(this, 0, nv.data(), &data_prd);
   } else {
-    rv = spdy_->submit_request(this, 0, nv.get(), 0);
+    rv = spdy_->submit_request(this, 0, nv.data(), nullptr);
   }
   if(rv != 0) {
     DCLOG(FATAL, this) << "nghttp2_submit_request() failed";