diff --git a/examples/client.c b/examples/client.c
index 5acac92a..305d79ef 100644
--- a/examples/client.c
+++ b/examples/client.c
@@ -613,8 +613,8 @@ static void fetch_uri(const struct URI *uri)
   connection.want_io = IO_NONE;
 
   /* Send connection header in blocking I/O mode */
-  SSL_write(ssl, NGHTTP2_CLIENT_CONNECTION_HEADER,
-            NGHTTP2_CLIENT_CONNECTION_HEADER_LEN);
+  SSL_write(ssl, NGHTTP2_CLIENT_CONNECTION_PREFACE,
+            NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN);
 
   /* Here make file descriptor non-block */
   make_non_block(fd);
diff --git a/examples/libevent-client.c b/examples/libevent-client.c
index 7734e607..2c635b8b 100644
--- a/examples/libevent-client.c
+++ b/examples/libevent-client.c
@@ -371,8 +371,8 @@ static void send_client_connection_header(http2_session_data *session_data)
   int rv;
 
   bufferevent_write(session_data->bev,
-                    NGHTTP2_CLIENT_CONNECTION_HEADER,
-                    NGHTTP2_CLIENT_CONNECTION_HEADER_LEN);
+                    NGHTTP2_CLIENT_CONNECTION_PREFACE,
+                    NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN);
   rv = nghttp2_submit_settings(session_data->session, NGHTTP2_FLAG_NONE,
                                iv, ARRLEN(iv));
   if(rv != 0) {
diff --git a/examples/libevent-server.c b/examples/libevent-server.c
index 2fcff6c0..fdf71852 100644
--- a/examples/libevent-server.c
+++ b/examples/libevent-server.c
@@ -190,7 +190,7 @@ static http2_session_data* create_http2_session_data(app_context *app_ctx,
     (app_ctx->evbase, fd, ssl,
      BUFFEREVENT_SSL_ACCEPTING,
      BEV_OPT_CLOSE_ON_FREE | BEV_OPT_DEFER_CALLBACKS);
-  session_data->handshake_leftlen = NGHTTP2_CLIENT_CONNECTION_HEADER_LEN;
+  session_data->handshake_leftlen = NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN;
   rv = getnameinfo(addr, addrlen, host, sizeof(host), NULL, 0, NI_NUMERICHOST);
   if(rv != 0) {
     session_data->client_addr = strdup("(unknown)");
@@ -629,9 +629,9 @@ static void handshake_readcb(struct bufferevent *bev, void *ptr)
   uint8_t data[24];
   struct evbuffer *input = bufferevent_get_input(session_data->bev);
   int readlen = evbuffer_remove(input, data, session_data->handshake_leftlen);
-  const char *conhead = NGHTTP2_CLIENT_CONNECTION_HEADER;
+  const char *conhead = NGHTTP2_CLIENT_CONNECTION_PREFACE;
 
-  if(memcmp(conhead + NGHTTP2_CLIENT_CONNECTION_HEADER_LEN
+  if(memcmp(conhead + NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN
             - session_data->handshake_leftlen, data, readlen) != 0) {
     delete_http2_session_data(session_data);
     return;
diff --git a/lib/includes/nghttp2/nghttp2.h b/lib/includes/nghttp2/nghttp2.h
index 1348024b..331ee4e4 100644
--- a/lib/includes/nghttp2/nghttp2.h
+++ b/lib/includes/nghttp2/nghttp2.h
@@ -135,18 +135,36 @@ typedef struct {
  */
 #define NGHTTP2_MAX_HEADER_TABLE_SIZE (1 << 16)
 
+
 /**
  * @macro
  *
- * The client connection header.
+ * The client connection preface.
  */
-#define NGHTTP2_CLIENT_CONNECTION_HEADER "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
+#define NGHTTP2_CLIENT_CONNECTION_PREFACE "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
+
+/**
+ * @macro
+ *
+ * The length of :macro:`NGHTTP2_CLIENT_CONNECTION_PREFACE`.
+ */
+#define NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN 24
+
+/**
+ * @macro
+ *
+ * The client connection header.  This macro is obsoleted by
+ * NGHTTP2_CLIENT_CONNECTION_PREFACE.
+ */
+#define NGHTTP2_CLIENT_CONNECTION_HEADER NGHTTP2_CLIENT_CONNECTION_PREFACE
+
 /**
  * @macro
  *
  * The length of :macro:`NGHTTP2_CLIENT_CONNECTION_HEADER`.
  */
-#define NGHTTP2_CLIENT_CONNECTION_HEADER_LEN 24
+#define NGHTTP2_CLIENT_CONNECTION_HEADER_LEN    \
+  NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN
 
 /**
  * @enum
diff --git a/python/cnghttp2.pxd b/python/cnghttp2.pxd
index b3ccb35d..9fefc832 100644
--- a/python/cnghttp2.pxd
+++ b/python/cnghttp2.pxd
@@ -25,7 +25,7 @@ from libc.stdint cimport uint8_t, uint16_t, uint32_t, int32_t
 cdef extern from 'nghttp2/nghttp2.h':
 
     const char NGHTTP2_PROTO_VERSION_ID[]
-    const char NGHTTP2_CLIENT_CONNECTION_HEADER[]
+    const char NGHTTP2_CLIENT_CONNECTION_PREFACE[]
     const size_t NGHTTP2_INITIAL_WINDOW_SIZE
 
     ctypedef struct nghttp2_session:
diff --git a/python/nghttp2.pyx b/python/nghttp2.pyx
index 596ac0a2..9741619c 100644
--- a/python/nghttp2.pyx
+++ b/python/nghttp2.pyx
@@ -901,7 +901,7 @@ if asyncio:
 
         def connection_made(self, transport):
             self.transport = transport
-            self.connection_header = cnghttp2.NGHTTP2_CLIENT_CONNECTION_HEADER
+            self.connection_header = cnghttp2.NGHTTP2_CLIENT_CONNECTION_PREFACE
             sock = self.transport.get_extra_info('socket')
             sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
             ssl_ctx = self.transport.get_extra_info('sslcontext')
diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index 161012ac..6cee9448 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -313,7 +313,7 @@ Http2Handler::Http2Handler(Sessions *sessions,
     settings_timerev_(nullptr),
     pending_data_(nullptr),
     pending_datalen_(0),
-    left_connhd_len_(NGHTTP2_CLIENT_CONNECTION_HEADER_LEN),
+    left_connhd_len_(NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN),
     fd_(fd)
 {
   nghttp2_buf_wrap_init(&sendbuf_, sendbufarray_, sizeof(sendbufarray_));
@@ -625,9 +625,9 @@ int Http2Handler::on_read()
 
   if(left_connhd_len_ > 0) {
     auto len = std::min(left_connhd_len_, nread);
-    const char *conhead = NGHTTP2_CLIENT_CONNECTION_HEADER;
+    const char *conhead = NGHTTP2_CLIENT_CONNECTION_PREFACE;
 
-    if(memcmp(conhead + NGHTTP2_CLIENT_CONNECTION_HEADER_LEN -
+    if(memcmp(conhead + NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN -
               left_connhd_len_, bufp, len) != 0) {
       return -1;
     }
diff --git a/src/h2load_http2_session.cc b/src/h2load_http2_session.cc
index 6df6435d..c5e2107f 100644
--- a/src/h2load_http2_session.cc
+++ b/src/h2load_http2_session.cc
@@ -135,8 +135,8 @@ void Http2Session::on_connect()
                                  extra_connection_window);
   }
 
-  bufferevent_write(client_->bev, NGHTTP2_CLIENT_CONNECTION_HEADER,
-                    NGHTTP2_CLIENT_CONNECTION_HEADER_LEN);
+  bufferevent_write(client_->bev, NGHTTP2_CLIENT_CONNECTION_PREFACE,
+                    NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN);
 }
 
 void Http2Session::submit_request()
diff --git a/src/nghttp.cc b/src/nghttp.cc
index 7a9871cd..18ea572d 100644
--- a/src/nghttp.cc
+++ b/src/nghttp.cc
@@ -713,8 +713,8 @@ struct HttpClient {
       }
     }
     // Send connection header here
-    bufferevent_write(bev, NGHTTP2_CLIENT_CONNECTION_HEADER,
-                      NGHTTP2_CLIENT_CONNECTION_HEADER_LEN);
+    bufferevent_write(bev, NGHTTP2_CLIENT_CONNECTION_PREFACE,
+                      NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN);
     // If upgrade succeeds, the SETTINGS value sent with
     // HTTP2-Settings header field has already been submitted to
     // session object.
diff --git a/src/shrpx_client_handler.cc b/src/shrpx_client_handler.cc
index e14c2238..3b6f2e40 100644
--- a/src/shrpx_client_handler.cc
+++ b/src/shrpx_client_handler.cc
@@ -138,7 +138,7 @@ namespace {
 void upstream_http2_connhd_readcb(bufferevent *bev, void *arg)
 {
   // This callback assumes upstream is Http2Upstream.
-  uint8_t data[NGHTTP2_CLIENT_CONNECTION_HEADER_LEN];
+  uint8_t data[NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN];
   auto handler = static_cast<ClientHandler*>(arg);
   auto leftlen = handler->get_left_connhd_len();
   auto input = bufferevent_get_input(bev);
@@ -147,8 +147,8 @@ void upstream_http2_connhd_readcb(bufferevent *bev, void *arg)
     delete handler;
     return;
   }
-  if(memcmp(NGHTTP2_CLIENT_CONNECTION_HEADER +
-            NGHTTP2_CLIENT_CONNECTION_HEADER_LEN - leftlen,
+  if(memcmp(NGHTTP2_CLIENT_CONNECTION_PREFACE +
+            NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN - leftlen,
             data, readlen) != 0) {
     // There is no downgrade path here. Just drop the connection.
     if(LOG_ENABLED(INFO)) {
@@ -175,7 +175,7 @@ namespace {
 void upstream_http1_connhd_readcb(bufferevent *bev, void *arg)
 {
   // This callback assumes upstream is HttpsUpstream.
-  uint8_t data[NGHTTP2_CLIENT_CONNECTION_HEADER_LEN];
+  uint8_t data[NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN];
   auto handler = static_cast<ClientHandler*>(arg);
   auto leftlen = handler->get_left_connhd_len();
   auto input = bufferevent_get_input(bev);
@@ -184,15 +184,15 @@ void upstream_http1_connhd_readcb(bufferevent *bev, void *arg)
     delete handler;
     return;
   }
-  if(memcmp(NGHTTP2_CLIENT_CONNECTION_HEADER +
-            NGHTTP2_CLIENT_CONNECTION_HEADER_LEN - leftlen,
+  if(memcmp(NGHTTP2_CLIENT_CONNECTION_PREFACE +
+            NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN - leftlen,
             data, readlen) != 0) {
     if(LOG_ENABLED(INFO)) {
       CLOG(INFO, handler) << "This is HTTP/1.1 connection, "
                           << "but may be upgraded to HTTP/2 later.";
     }
     // Reset header length for later HTTP/2 upgrade
-    handler->set_left_connhd_len(NGHTTP2_CLIENT_CONNECTION_HEADER_LEN);
+    handler->set_left_connhd_len(NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN);
     handler->set_bev_cb(upstream_readcb, upstream_writecb, upstream_eventcb);
     if(handler->on_read() != 0) {
       delete handler;
@@ -254,7 +254,7 @@ ClientHandler::ClientHandler(bufferevent *bev,
     bev_(bev),
     http2session_(nullptr),
     ssl_(ssl),
-    left_connhd_len_(NGHTTP2_CLIENT_CONNECTION_HEADER_LEN),
+    left_connhd_len_(NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN),
     fd_(fd),
     should_close_after_write_(false),
     tls_handshake_(false),
diff --git a/src/shrpx_http2_session.cc b/src/shrpx_http2_session.cc
index bda23d38..30791478 100644
--- a/src/shrpx_http2_session.cc
+++ b/src/shrpx_http2_session.cc
@@ -1219,8 +1219,8 @@ int Http2Session::on_connect()
     }
   }
 
-  rv = bufferevent_write(bev_, NGHTTP2_CLIENT_CONNECTION_HEADER,
-                         NGHTTP2_CLIENT_CONNECTION_HEADER_LEN);
+  rv = bufferevent_write(bev_, NGHTTP2_CLIENT_CONNECTION_PREFACE,
+                         NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN);
   if(rv != 0) {
     SSLOG(FATAL, this) << "bufferevent_write() failed";
     return -1;