diff --git a/lib/includes/nghttp2/nghttp2.h b/lib/includes/nghttp2/nghttp2.h
index 8674ce26..e06a850b 100644
--- a/lib/includes/nghttp2/nghttp2.h
+++ b/lib/includes/nghttp2/nghttp2.h
@@ -1550,6 +1550,38 @@ void* nghttp2_session_get_stream_user_data(nghttp2_session *session,
  */
 size_t nghttp2_session_get_outbound_queue_size(nghttp2_session *session);
 
+/**
+ * @function
+ *
+ * Returns the number of DATA payload in bytes received without
+ * WINDOW_UPDATE transmission for the stream |stream_id|. The local
+ * (receive) window size can be adjusted by
+ * `nghttp2_submit_window_update()`. This function takes into account
+ * that and returns effective data length. In particular, if the
+ * local window size is reduced by submitting negative
+ * window_size_increment with `nghttp2_submit_window_update()`, this
+ * function returns the number of bytes less than actually received.
+ *
+ * If flow control is disabled for that stream, this function returns
+ * 0.
+ *
+ * This function returns -1 if it fails.
+ */
+int32_t nghttp2_session_get_stream_effective_recv_data_length
+(nghttp2_session *session, int32_t stream_id);
+
+/**
+ * @function
+ *
+ * Returns the local (receive) window size. The local window size can
+ * be adjusted by `nghttp2_submit_window_update()`. This function
+ * takes into account that and returns effective window size.
+ *
+ * This function returns -1 if it fails.
+ */
+int32_t nghttp2_session_get_stream_effective_local_window_size
+(nghttp2_session *session, int32_t stream_id);
+
 /**
  * @function
  *
diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index a6b5b843..9e1dc262 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -3571,6 +3571,31 @@ size_t nghttp2_session_get_outbound_queue_size(nghttp2_session *session)
   return nghttp2_pq_size(&session->ob_pq)+nghttp2_pq_size(&session->ob_ss_pq);
 }
 
+int32_t nghttp2_session_get_stream_effective_recv_data_length
+(nghttp2_session *session, int32_t stream_id)
+{
+  nghttp2_stream *stream;
+  stream = nghttp2_session_get_stream(session, stream_id);
+  if(stream == NULL) {
+    return -1;
+  }
+  if(stream->local_flow_control == 0) {
+    return 0;
+  }
+  return stream->recv_window_size;
+}
+
+int32_t nghttp2_session_get_stream_effective_local_window_size
+(nghttp2_session *session, int32_t stream_id)
+{
+  nghttp2_stream *stream;
+  stream = nghttp2_session_get_stream(session, stream_id);
+  if(stream == NULL) {
+    return -1;
+  }
+  return stream->local_window_size;
+}
+
 int nghttp2_session_set_option(nghttp2_session *session,
                                int optname, void *optval, size_t optlen)
 {
diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index 14dd3b14..513c0e21 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -723,12 +723,13 @@ int Http2Upstream::rst_stream(Downstream *downstream,
   return 0;
 }
 
-int Http2Upstream::window_update(Downstream *downstream)
+int Http2Upstream::window_update(Downstream *downstream,
+                                 int32_t window_size_increment)
 {
   int rv;
   rv = nghttp2_submit_window_update(session_, NGHTTP2_FLAG_NONE,
                                     downstream->get_stream_id(),
-                                    downstream->get_recv_window_size());
+                                    window_size_increment);
   downstream->set_recv_window_size(0);
   if(rv < NGHTTP2_ERR_FATAL) {
     ULOG(FATAL, this) << "nghttp2_submit_window_update() failed: "
@@ -962,8 +963,15 @@ void Http2Upstream::pause_read(IOCtrlReason reason)
 int Http2Upstream::resume_read(IOCtrlReason reason, Downstream *downstream)
 {
   if(get_flow_control()) {
-    if(downstream->get_recv_window_size() >= get_initial_window_size()/2) {
-      window_update(downstream);
+    int32_t recv_length, window_size;
+    recv_length = nghttp2_session_get_stream_effective_recv_data_length
+      (session_, downstream->get_stream_id());
+    window_size = nghttp2_session_get_stream_effective_local_window_size
+      (session_, downstream->get_stream_id());
+    if(recv_length != -1 && window_size != -1) {
+      if(recv_length >= window_size / 2) {
+        window_update(downstream, recv_length);
+      }
     }
   }
   return send();
diff --git a/src/shrpx_http2_upstream.h b/src/shrpx_http2_upstream.h
index e63dc27a..1d0c02a1 100644
--- a/src/shrpx_http2_upstream.h
+++ b/src/shrpx_http2_upstream.h
@@ -58,7 +58,7 @@ public:
   nghttp2_session* get_spdy_session();
 
   int rst_stream(Downstream *downstream, nghttp2_error_code error_code);
-  int window_update(Downstream *downstream);
+  int window_update(Downstream *downstream, int32_t window_size_increment);
   int error_reply(Downstream *downstream, unsigned int status_code);
 
   virtual void pause_read(IOCtrlReason reason);
diff --git a/src/shrpx_spdy_downstream_connection.cc b/src/shrpx_spdy_downstream_connection.cc
index f79e8724..a9b76379 100644
--- a/src/shrpx_spdy_downstream_connection.cc
+++ b/src/shrpx_spdy_downstream_connection.cc
@@ -442,14 +442,20 @@ int SpdyDownstreamConnection::resume_read(IOCtrlReason reason)
   int rv;
   if(spdy_->get_state() == SpdySession::CONNECTED &&
      spdy_->get_flow_control() &&
-     downstream_ && downstream_->get_downstream_stream_id() != -1 &&
-     recv_window_size_ >= spdy_->get_initial_window_size()/2) {
-    rv = spdy_->submit_window_update(this, recv_window_size_);
-    if(rv == -1) {
-      return -1;
+     downstream_ && downstream_->get_downstream_stream_id() != -1) {
+    int32_t recv_length, window_size;
+    recv_length = spdy_->get_stream_effective_recv_data_length
+      (downstream_->get_stream_id());
+    window_size = spdy_->get_stream_effective_local_window_size
+      (downstream_->get_stream_id());
+    if(recv_length >= window_size / 2) {
+      rv = spdy_->submit_window_update(this, recv_length);
+      if(rv == -1) {
+        return -1;
+      }
+      spdy_->notify();
+      recv_window_size_ = 0;
     }
-    spdy_->notify();
-    recv_window_size_ = 0;
   }
   return 0;
 }
diff --git a/src/shrpx_spdy_session.cc b/src/shrpx_spdy_session.cc
index a71a740a..5e2c73a4 100644
--- a/src/shrpx_spdy_session.cc
+++ b/src/shrpx_spdy_session.cc
@@ -618,6 +618,18 @@ int32_t SpdySession::get_initial_window_size() const
   return (1 << get_config()->spdy_downstream_window_bits) - 1;
 }
 
+int32_t SpdySession::get_stream_effective_recv_data_length(int32_t stream_id)
+{
+  return nghttp2_session_get_stream_effective_recv_data_length
+    (session_, stream_id);
+}
+
+int32_t SpdySession::get_stream_effective_local_window_size(int32_t stream_id)
+{
+  return nghttp2_session_get_stream_effective_local_window_size
+    (session_, stream_id);
+}
+
 bool SpdySession::get_flow_control() const
 {
   return flow_control_;
diff --git a/src/shrpx_spdy_session.h b/src/shrpx_spdy_session.h
index c1eb80ab..4e6d93b4 100644
--- a/src/shrpx_spdy_session.h
+++ b/src/shrpx_spdy_session.h
@@ -74,6 +74,9 @@ public:
 
   int32_t get_initial_window_size() const;
 
+  int32_t get_stream_effective_recv_data_length(int32_t stream_id);
+  int32_t get_stream_effective_local_window_size(int32_t stream_id);
+
   bool get_flow_control() const;
 
   int resume_data(SpdyDownstreamConnection *dconn);