diff --git a/src/shrpx_http2_session.cc b/src/shrpx_http2_session.cc
index 3de70cc4..81bba699 100644
--- a/src/shrpx_http2_session.cc
+++ b/src/shrpx_http2_session.cc
@@ -57,6 +57,7 @@ Http2Session::Http2Session(event_base *evbase, SSL_CTX *ssl_ctx)
     wrbev_(nullptr),
     rdbev_(nullptr),
     settings_timerev_(nullptr),
+    recv_ign_window_size_(0),
     fd_(-1),
     state_(DISCONNECTED),
     notified_(false),
@@ -668,6 +669,7 @@ int Http2Session::submit_window_update(Http2DownstreamConnection *dconn,
     stream_id = dconn->get_downstream()->get_downstream_stream_id();
   } else {
     stream_id = 0;
+    recv_ign_window_size_ = 0;
   }
   rv = nghttp2_submit_window_update(session_, NGHTTP2_FLAG_NONE,
                                     stream_id, amount);
@@ -1101,11 +1103,13 @@ int on_data_chunk_recv_callback(nghttp2_session *session,
     (nghttp2_session_get_stream_user_data(session, stream_id));
   if(!sd || !sd->dconn) {
     http2session->submit_rst_stream(stream_id, NGHTTP2_INTERNAL_ERROR);
+    http2session->handle_ign_data_chunk(len);
     return 0;
   }
   auto downstream = sd->dconn->get_downstream();
   if(!downstream || downstream->get_downstream_stream_id() != stream_id) {
     http2session->submit_rst_stream(stream_id, NGHTTP2_INTERNAL_ERROR);
+    http2session->handle_ign_data_chunk(len);
     return 0;
   }
 
@@ -1113,6 +1117,7 @@ int on_data_chunk_recv_callback(nghttp2_session *session,
   rv = upstream->on_downstream_body(downstream, data, len, false);
   if(rv != 0) {
     http2session->submit_rst_stream(stream_id, NGHTTP2_INTERNAL_ERROR);
+    http2session->handle_ign_data_chunk(len);
     downstream->set_response_state(Downstream::MSG_RESET);
   }
   call_downstream_readcb(http2session, downstream);
@@ -1454,4 +1459,19 @@ SSL* Http2Session::get_ssl() const
   return ssl_;
 }
 
+int Http2Session::handle_ign_data_chunk(size_t len)
+{
+  int32_t window_size;
+
+  recv_ign_window_size_ += len;
+
+  window_size = nghttp2_session_get_effective_local_window_size(session_);
+
+  if(recv_ign_window_size_ >= window_size / 2) {
+    submit_window_update(nullptr, recv_ign_window_size_);
+  }
+
+  return 0;
+}
+
 } // namespace shrpx
diff --git a/src/shrpx_http2_session.h b/src/shrpx_http2_session.h
index 85b9e697..9a5d6a9a 100644
--- a/src/shrpx_http2_session.h
+++ b/src/shrpx_http2_session.h
@@ -108,6 +108,8 @@ public:
 
   SSL* get_ssl() const;
 
+  int handle_ign_data_chunk(size_t len);
+
   enum {
     // Disconnected
     DISCONNECTED,
@@ -138,6 +140,7 @@ private:
   bufferevent *wrbev_;
   bufferevent *rdbev_;
   event *settings_timerev_;
+  int32_t recv_ign_window_size_;
   // fd_ is used for proxy connection and no TLS connection. For
   // direct or TLS connection, it may be -1 even after connection is
   // established. Use bufferevent_getfd(bev_) to get file descriptor