diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index 5070a26b..4f515e54 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -856,10 +856,9 @@ int Http2Handler::connection_made() {
   }
 
   if (config->connection_window_bits != -1) {
-    r = nghttp2_submit_window_update(
+    r = nghttp2_session_set_local_window_size(
         session_, NGHTTP2_FLAG_NONE, 0,
-        (1 << config->connection_window_bits) - 1 -
-            NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE);
+        (1 << config->connection_window_bits) - 1);
     if (r != 0) {
       return r;
     }
diff --git a/src/asio_client_session_impl.cc b/src/asio_client_session_impl.cc
index fade97bd..fafb26b1 100644
--- a/src/asio_client_session_impl.cc
+++ b/src/asio_client_session_impl.cc
@@ -373,9 +373,8 @@ bool session_impl::setup_session() {
        {NGHTTP2_SETTINGS_INITIAL_WINDOW_SIZE, window_size}}};
   nghttp2_submit_settings(session_, NGHTTP2_FLAG_NONE, iv.data(), iv.size());
   // increase connection window size up to window_size
-  nghttp2_submit_window_update(session_, NGHTTP2_FLAG_NONE, 0,
-                               window_size -
-                                   NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE);
+  nghttp2_session_set_local_window_size(session_, NGHTTP2_FLAG_NONE, 0,
+                                        window_size);
   return true;
 }
 
diff --git a/src/h2load_http2_session.cc b/src/h2load_http2_session.cc
index ea71d66a..5e333964 100644
--- a/src/h2load_http2_session.cc
+++ b/src/h2load_http2_session.cc
@@ -219,13 +219,10 @@ void Http2Session::on_connect() {
 
   assert(rv == 0);
 
-  auto extra_connection_window =
-      (1 << client_->worker->config->connection_window_bits) - 1 -
-      NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE;
-  if (extra_connection_window != 0) {
-    nghttp2_submit_window_update(session_, NGHTTP2_FLAG_NONE, 0,
-                                 extra_connection_window);
-  }
+  auto connection_window =
+      (1 << client_->worker->config->connection_window_bits) - 1;
+  nghttp2_session_set_local_window_size(session_, NGHTTP2_FLAG_NONE, 0,
+                                        connection_window);
 
   client_->signal_write();
 }
diff --git a/src/nghttp.cc b/src/nghttp.cc
index 2c427947..c78c10bf 100644
--- a/src/nghttp.cc
+++ b/src/nghttp.cc
@@ -1151,9 +1151,9 @@ int HttpClient::connection_made() {
   ev_timer_again(loop, &settings_timer);
 
   if (config.connection_window_bits != -1) {
-    int32_t wininc = (1 << config.connection_window_bits) - 1 -
-                     NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE;
-    rv = nghttp2_submit_window_update(session, NGHTTP2_FLAG_NONE, 0, wininc);
+    int32_t window_size = (1 << config.connection_window_bits) - 1;
+    rv = nghttp2_session_set_local_window_size(session, NGHTTP2_FLAG_NONE, 0,
+                                               window_size);
     if (rv != 0) {
       return -1;
     }
diff --git a/src/shrpx_http2_session.cc b/src/shrpx_http2_session.cc
index a0361be9..bba56fa3 100644
--- a/src/shrpx_http2_session.cc
+++ b/src/shrpx_http2_session.cc
@@ -1533,11 +1533,11 @@ int Http2Session::connection_made() {
     return -1;
   }
 
-  auto connection_window_bits = http2conf.downstream.connection_window_bits;
-  if (connection_window_bits > 16) {
-    int32_t delta = (1 << connection_window_bits) - 1 -
-                    NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE;
-    rv = nghttp2_submit_window_update(session_, NGHTTP2_FLAG_NONE, 0, delta);
+  if (http2conf.downstream.connection_window_bits != 16) {
+    int32_t window_size =
+        (1 << http2conf.downstream.connection_window_bits) - 1;
+    rv = nghttp2_session_set_local_window_size(session_, NGHTTP2_FLAG_NONE, 0,
+                                               window_size);
     if (rv != 0) {
       return -1;
     }
diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index f603bd04..6c8cc6f8 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -883,10 +883,10 @@ Http2Upstream::Http2Upstream(ClientHandler *handler)
                       << nghttp2_strerror(rv);
   }
 
-  if (http2conf.upstream.connection_window_bits > 16) {
-    int32_t delta = (1 << http2conf.upstream.connection_window_bits) - 1 -
-                    NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE;
-    rv = nghttp2_submit_window_update(session_, NGHTTP2_FLAG_NONE, 0, delta);
+  if (http2conf.upstream.connection_window_bits != 16) {
+    int32_t window_size = (1 << http2conf.upstream.connection_window_bits) - 1;
+    rv = nghttp2_session_set_local_window_size(session_, NGHTTP2_FLAG_NONE, 0,
+                                               window_size);
 
     if (rv != 0) {
       ULOG(ERROR, this) << "nghttp2_submit_window_update() returned error: "