diff --git a/lib/includes/nghttp2/nghttp2.h b/lib/includes/nghttp2/nghttp2.h
index d3f81a30..9c580a3f 100644
--- a/lib/includes/nghttp2/nghttp2.h
+++ b/lib/includes/nghttp2/nghttp2.h
@@ -341,7 +341,12 @@ typedef enum {
   /**
    * The user callback function failed.  This is a fatal error.
    */
-  NGHTTP2_ERR_CALLBACK_FAILURE = -902
+  NGHTTP2_ERR_CALLBACK_FAILURE = -902,
+  /**
+   * Invalid connection preface was received and further processing is
+   * not possible.
+   */
+  NGHTTP2_ERR_BAD_PREFACE = -903
 } nghttp2_error;
 
 /**
@@ -1736,6 +1741,24 @@ void nghttp2_option_set_no_auto_window_update(nghttp2_option *option, int val);
 void nghttp2_option_set_peer_max_concurrent_streams(nghttp2_option *option,
                                                     uint32_t val);
 
+/**
+ * @function
+ *
+ * By default, nghttp2 library only handles HTTP/2 frames and does not
+ * recognize first 24 bytes of client connection preface.  This design
+ * choice is done due to the fact that server may want to detect the
+ * application protocol based on first few bytes on clear text
+ * communication.  But for simple servers which only speak HTTP/2, it
+ * is easier for developers if nghttp2 library takes care of client
+ * connection preface.
+ *
+ * If this option is used with nonzero |val|, nghttp2 library checks
+ * first 24 bytes client connection preface.  If it is not a valid
+ * one, `nghttp2_session_recv()` and `nghttp2_session_mem_recv()` will
+ * return error :enum:`NGHTTP2_ERR_BAD_PREFACE`, which is fatal error.
+ */
+void nghttp2_option_set_recv_client_preface(nghttp2_option *option, int val);
+
 /**
  * @function
  *
@@ -1986,6 +2009,10 @@ ssize_t nghttp2_session_mem_send(nghttp2_session *session,
  *     Out of memory.
  * :enum:`NGHTTP2_ERR_CALLBACK_FAILURE`
  *     The callback function failed.
+ * :enum:`NGHTTP2_ERR_BAD_PREFACE`
+ *     Invalid client preface was detected.  This error only returns
+ *     when |session| was configured as server and
+ *     `nghttp2_option_set_recv_client_preface()` is used.
  */
 int nghttp2_session_recv(nghttp2_session *session);
 
@@ -2017,6 +2044,10 @@ int nghttp2_session_recv(nghttp2_session *session);
  *     Out of memory.
  * :enum:`NGHTTP2_ERR_CALLBACK_FAILURE`
  *     The callback function failed.
+ * :enum:`NGHTTP2_ERR_BAD_PREFACE`
+ *     Invalid client preface was detected.  This error only returns
+ *     when |session| was configured as server and
+ *     `nghttp2_option_set_recv_client_preface()` is used.
  */
 ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
                                  const uint8_t *in, size_t inlen);
diff --git a/lib/nghttp2_option.c b/lib/nghttp2_option.c
index adb59bc0..914714a1 100644
--- a/lib/nghttp2_option.c
+++ b/lib/nghttp2_option.c
@@ -52,3 +52,10 @@ void nghttp2_option_set_peer_max_concurrent_streams(nghttp2_option *option,
   option->opt_set_mask |= NGHTTP2_OPT_PEER_MAX_CONCURRENT_STREAMS;
   option->peer_max_concurrent_streams = val;
 }
+
+void nghttp2_option_set_recv_client_preface
+(nghttp2_option *option, int val)
+{
+  option->opt_set_mask |= NGHTTP2_OPT_RECV_CLIENT_PREFACE;
+  option->recv_client_preface = val;
+}
diff --git a/lib/nghttp2_option.h b/lib/nghttp2_option.h
index d5bad011..aefd87be 100644
--- a/lib/nghttp2_option.h
+++ b/lib/nghttp2_option.h
@@ -56,7 +56,8 @@ typedef enum {
    * will be overwritten if the local endpoint receives
    * SETTINGS_MAX_CONCURRENT_STREAMS from the remote endpoint.
    */
-  NGHTTP2_OPT_PEER_MAX_CONCURRENT_STREAMS = 1 << 1
+  NGHTTP2_OPT_PEER_MAX_CONCURRENT_STREAMS = 1 << 1,
+  NGHTTP2_OPT_RECV_CLIENT_PREFACE = 1 << 2,
 } nghttp2_option_flag;
 
 /**
@@ -76,6 +77,10 @@ struct nghttp2_option {
    * NGHTTP2_OPT_NO_AUTO_WINDOW_UPDATE
    */
   uint8_t no_auto_window_update;
+  /**
+   * NGHTTP2_OPT_RECV_CLIENT_PREFACE
+   */
+  uint8_t recv_client_preface;
 };
 
 #endif /* NGHTTP2_OPTION_H */
diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index e0711281..d156800a 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -398,6 +398,12 @@ static int session_new(nghttp2_session **session_ptr,
         option->peer_max_concurrent_streams;
 
     }
+
+    if(option->opt_set_mask & NGHTTP2_OPT_RECV_CLIENT_PREFACE) {
+
+      (*session_ptr)->opt_flags |= NGHTTP2_OPTMASK_RECV_CLIENT_PREFACE;
+
+    }
   }
 
   (*session_ptr)->callbacks = *callbacks;
@@ -405,6 +411,15 @@ static int session_new(nghttp2_session **session_ptr,
 
   session_inbound_frame_reset(*session_ptr);
 
+  if(server &&
+     ((*session_ptr)->opt_flags & NGHTTP2_OPTMASK_RECV_CLIENT_PREFACE)) {
+
+    nghttp2_inbound_frame *iframe = &(*session_ptr)->iframe;
+
+    iframe->state = NGHTTP2_IB_READ_CLIENT_PREFACE;
+    iframe->payloadleft = NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN;
+  }
+
   return 0;
 
  fail_aob_framebuf:
@@ -4338,6 +4353,23 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
 
   for(;;) {
     switch(iframe->state) {
+    case NGHTTP2_IB_READ_CLIENT_PREFACE:
+      readlen = nghttp2_min(inlen, iframe->payloadleft);
+
+      if(memcmp(NGHTTP2_CLIENT_CONNECTION_PREFACE +
+                NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN - iframe->payloadleft,
+                in, readlen) != 0) {
+        return NGHTTP2_ERR_BAD_PREFACE;
+      }
+
+      iframe->payloadleft -= readlen;
+      in += readlen;
+
+      if(iframe->payloadleft == 0) {
+        session_inbound_frame_reset(session);
+      }
+
+      break;
     case NGHTTP2_IB_READ_HEAD: {
       int on_begin_frame_called = 0;
 
diff --git a/lib/nghttp2_session.h b/lib/nghttp2_session.h
index ac60dd96..4c6943ee 100644
--- a/lib/nghttp2_session.h
+++ b/lib/nghttp2_session.h
@@ -45,6 +45,7 @@
  */
 typedef enum {
   NGHTTP2_OPTMASK_NO_AUTO_WINDOW_UPDATE = 1 << 0,
+  NGHTTP2_OPTMASK_RECV_CLIENT_PREFACE = 1 << 1,
 } nghttp2_optmask;
 
 typedef enum {
@@ -65,6 +66,7 @@ typedef struct {
 /* Internal state when receiving incoming frame */
 typedef enum {
   /* Receiving frame header */
+  NGHTTP2_IB_READ_CLIENT_PREFACE,
   NGHTTP2_IB_READ_HEAD,
   NGHTTP2_IB_READ_NBYTE,
   NGHTTP2_IB_READ_HEADER_BLOCK,
diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index e992b44a..b93e6744 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -104,6 +104,7 @@ void append_nv(Stream *stream, const std::vector<nghttp2_nv>& nva)
 Config::Config()
   : stream_read_timeout{60, 0},
     stream_write_timeout{60, 0},
+    session_option(nullptr),
     data_ptr(nullptr),
     padding(0),
     num_worker(1),
@@ -115,7 +116,10 @@ Config::Config()
     no_tls(false),
     error_gzip(false),
     early_response(false)
-{}
+{
+  nghttp2_option_new(&session_option);
+  nghttp2_option_set_recv_client_preface(session_option, 1);
+}
 
 Stream::Stream(Http2Handler *handler, int32_t stream_id)
   : handler(handler),
@@ -337,7 +341,6 @@ Http2Handler::Http2Handler(Sessions *sessions,
     settings_timerev_(nullptr),
     pending_data_(nullptr),
     pending_datalen_(0),
-    left_connhd_len_(NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN),
     fd_(fd)
 {
   nghttp2_buf_wrap_init(&sendbuf_, sendbufarray_, sizeof(sendbufarray_));
@@ -651,27 +654,6 @@ int Http2Handler::on_read()
   nread = rv;
   bufp = buf;
 
-  if(left_connhd_len_ > 0) {
-    auto len = std::min(left_connhd_len_, nread);
-    const char *conhead = NGHTTP2_CLIENT_CONNECTION_PREFACE;
-
-    if(memcmp(conhead + NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN -
-              left_connhd_len_, bufp, len) != 0) {
-      return -1;
-    }
-
-    left_connhd_len_ -= len;
-    nread -= len;
-
-    if(nread == 0) {
-      wait_events();
-
-      return 0;
-    }
-
-    bufp += len;
-  }
-
   rv = nghttp2_session_mem_recv(session_, bufp, nread);
   if(rv < 0) {
     std::cerr << "nghttp2_session_mem_recv() returned error: "
@@ -736,7 +718,8 @@ int Http2Handler::on_connect()
 {
   int r;
 
-  r = nghttp2_session_server_new(&session_, sessions_->get_callbacks(), this);
+  r = nghttp2_session_server_new2(&session_, sessions_->get_callbacks(), this,
+                                  sessions_->get_config()->session_option);
   if(r != 0) {
     return r;
   }
@@ -947,16 +930,6 @@ const Config* Http2Handler::get_config() const
   return sessions_->get_config();
 }
 
-size_t Http2Handler::get_left_connhd_len() const
-{
-  return left_connhd_len_;
-}
-
-void Http2Handler::set_left_connhd_len(size_t left)
-{
-  left_connhd_len_ = left;
-}
-
 void Http2Handler::remove_settings_timer()
 {
   if(settings_timerev_) {
diff --git a/src/HttpServer.h b/src/HttpServer.h
index d7e3fa70..09b63975 100644
--- a/src/HttpServer.h
+++ b/src/HttpServer.h
@@ -66,6 +66,7 @@ struct Config {
   std::string dh_param_file;
   timeval stream_read_timeout;
   timeval stream_write_timeout;
+  nghttp2_option *session_option;
   void *data_ptr;
   size_t padding;
   size_t num_worker;
@@ -138,8 +139,6 @@ public:
   int64_t session_id() const;
   Sessions* get_sessions() const;
   const Config* get_config() const;
-  size_t get_left_connhd_len() const;
-  void set_left_connhd_len(size_t left);
   void remove_settings_timer();
   void terminate_session(uint32_t error_code);
   int tls_handshake();
@@ -159,7 +158,6 @@ private:
   event *settings_timerev_;
   const uint8_t *pending_data_;
   size_t pending_datalen_;
-  size_t left_connhd_len_;
   int fd_;
   uint8_t sendbufarray_[65536];
 };
diff --git a/tests/main.c b/tests/main.c
index 4338ec04..1c8f3e6f 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -243,6 +243,8 @@ int main(int argc, char* argv[])
                    test_nghttp2_session_graceful_shutdown) ||
       !CU_add_test(pSuite, "session_on_header_temporal_failure",
                    test_nghttp2_session_on_header_temporal_failure) ||
+      !CU_add_test(pSuite, "session_recv_client_preface",
+                   test_nghttp2_session_recv_client_preface) ||
       !CU_add_test(pSuite, "frame_pack_headers",
                    test_nghttp2_frame_pack_headers) ||
       !CU_add_test(pSuite, "frame_pack_headers_frame_too_large",
diff --git a/tests/nghttp2_session_test.c b/tests/nghttp2_session_test.c
index b11930fc..9bca793c 100644
--- a/tests/nghttp2_session_test.c
+++ b/tests/nghttp2_session_test.c
@@ -6400,3 +6400,52 @@ void test_nghttp2_session_on_header_temporal_failure(void)
   nghttp2_hd_deflate_free(&deflater);
   nghttp2_session_del(session);
 }
+
+void test_nghttp2_session_recv_client_preface(void)
+{
+  nghttp2_session *session;
+  nghttp2_session_callbacks callbacks;
+  nghttp2_option *option;
+  ssize_t rv;
+
+  memset(&callbacks, 0, sizeof(callbacks));
+
+  nghttp2_option_new(&option);
+  nghttp2_option_set_recv_client_preface(option, 1);
+
+  /* Check success case */
+  nghttp2_session_server_new2(&session, &callbacks, NULL, option);
+
+  CU_ASSERT(session->opt_flags & NGHTTP2_OPTMASK_RECV_CLIENT_PREFACE);
+
+  rv = nghttp2_session_mem_recv
+    (session,
+     (const uint8_t*)NGHTTP2_CLIENT_CONNECTION_PREFACE,
+     NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN);
+
+  CU_ASSERT(rv == NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN);
+  CU_ASSERT(NGHTTP2_IB_READ_HEAD == session->iframe.state);
+
+  nghttp2_session_del(session);
+
+  /* Check bad case */
+  nghttp2_session_server_new2(&session, &callbacks, NULL, option);
+
+  /* Feed preface with one byte less */
+  rv = nghttp2_session_mem_recv
+    (session,
+     (const uint8_t*)NGHTTP2_CLIENT_CONNECTION_PREFACE,
+     NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN - 1);
+
+  CU_ASSERT(rv == NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN - 1);
+  CU_ASSERT(NGHTTP2_IB_READ_CLIENT_PREFACE == session->iframe.state);
+  CU_ASSERT(1 == session->iframe.payloadleft);
+
+  rv = nghttp2_session_mem_recv(session, (const uint8_t*)"\0", 1);
+
+  CU_ASSERT(NGHTTP2_ERR_BAD_PREFACE == rv);
+
+  nghttp2_session_del(session);
+
+  nghttp2_option_del(option);
+}
diff --git a/tests/nghttp2_session_test.h b/tests/nghttp2_session_test.h
index 4b1be44b..af54d3ac 100644
--- a/tests/nghttp2_session_test.h
+++ b/tests/nghttp2_session_test.h
@@ -113,5 +113,6 @@ void test_nghttp2_session_stream_attach_data_subtree(void);
 void test_nghttp2_session_keep_closed_stream(void);
 void test_nghttp2_session_graceful_shutdown(void);
 void test_nghttp2_session_on_header_temporal_failure(void);
+void test_nghttp2_session_recv_client_preface(void);
 
 #endif /* NGHTTP2_SESSION_TEST_H */