diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index 713e71bd..034ae11d 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -3582,7 +3582,7 @@ int32_t nghttp2_session_get_stream_effective_recv_data_length
   if(stream->local_flow_control == 0) {
     return 0;
   }
-  return stream->recv_window_size;
+  return stream->recv_window_size < 0 ? 0 : stream->recv_window_size;
 }
 
 int32_t nghttp2_session_get_stream_effective_local_window_size
@@ -3602,7 +3602,7 @@ int32_t nghttp2_session_get_effective_recv_data_length
   if(session->local_flow_control == 0) {
     return 0;
   }
-  return session->recv_window_size;
+  return session->recv_window_size < 0 ? 0 : session->recv_window_size;
 }
 
 int32_t nghttp2_session_get_effective_local_window_size
diff --git a/tests/main.c b/tests/main.c
index 3d4865d2..9a4fd601 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -193,6 +193,8 @@ int main(int argc, char* argv[])
                    test_nghttp2_session_on_ctrl_not_send) ||
       !CU_add_test(pSuite, "session_get_outbound_queue_size",
                    test_nghttp2_session_get_outbound_queue_size) ||
+      !CU_add_test(pSuite, "session_get_effective_local_window_size",
+                   test_nghttp2_session_get_effective_local_window_size) ||
       !CU_add_test(pSuite, "session_set_option",
                    test_nghttp2_session_set_option) ||
       !CU_add_test(pSuite, "session_data_backoff_by_high_pri_frame",
diff --git a/tests/nghttp2_session_test.c b/tests/nghttp2_session_test.c
index 1fd5ac84..f9738bcf 100644
--- a/tests/nghttp2_session_test.c
+++ b/tests/nghttp2_session_test.c
@@ -3482,6 +3482,79 @@ void test_nghttp2_session_get_outbound_queue_size(void)
   nghttp2_session_del(session);
 }
 
+void test_nghttp2_session_get_effective_local_window_size(void)
+{
+  nghttp2_session *session;
+  nghttp2_session_callbacks callbacks;
+  nghttp2_stream *stream;
+
+  memset(&callbacks, 0, sizeof(nghttp2_session_callbacks));
+  CU_ASSERT(0 == nghttp2_session_client_new(&session, &callbacks, NULL));
+
+  stream = nghttp2_session_open_stream(session, 1, NGHTTP2_FLAG_NONE,
+                                       NGHTTP2_PRI_DEFAULT,
+                                       NGHTTP2_STREAM_OPENED, NULL);
+
+  CU_ASSERT(NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE ==
+            nghttp2_session_get_effective_local_window_size(session));
+  CU_ASSERT(0 == nghttp2_session_get_effective_recv_data_length(session));
+
+  CU_ASSERT(NGHTTP2_INITIAL_WINDOW_SIZE ==
+            nghttp2_session_get_stream_effective_local_window_size
+            (session, 1));
+  CU_ASSERT(0 ==
+            nghttp2_session_get_stream_effective_recv_data_length(session, 1));
+
+  /* Check connection flow control */
+  session->recv_window_size = 100;
+  nghttp2_submit_window_update(session, NGHTTP2_FLAG_NONE, 0, 1100);
+
+  CU_ASSERT(NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE + 1000 ==
+            nghttp2_session_get_effective_local_window_size(session));
+  CU_ASSERT(0 == nghttp2_session_get_effective_recv_data_length(session));
+
+  nghttp2_submit_window_update(session, NGHTTP2_FLAG_NONE, 0, -50);
+  /* Now session->recv_window_size = -50 */
+  CU_ASSERT(NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE + 950 ==
+            nghttp2_session_get_effective_local_window_size(session));
+  CU_ASSERT(0 == nghttp2_session_get_effective_recv_data_length(session));
+
+  session->recv_window_size += 50;
+  /* Now session->recv_window_size = 0 */
+  nghttp2_submit_window_update(session, NGHTTP2_FLAG_NONE, 0, 100);
+  CU_ASSERT(NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE + 1050 ==
+            nghttp2_session_get_effective_local_window_size(session));
+  CU_ASSERT(50 == nghttp2_session_get_effective_recv_data_length(session));
+
+  /* Check stream flow control */
+  stream->recv_window_size = 100;
+  nghttp2_submit_window_update(session, NGHTTP2_FLAG_NONE, 1, 1100);
+
+  CU_ASSERT(NGHTTP2_INITIAL_WINDOW_SIZE + 1000 ==
+            nghttp2_session_get_stream_effective_local_window_size
+            (session, 1));
+  CU_ASSERT(0 == nghttp2_session_get_stream_effective_recv_data_length
+            (session, 1));
+
+  nghttp2_submit_window_update(session, NGHTTP2_FLAG_NONE, 1, -50);
+  /* Now stream->recv_window_size = -50 */
+  CU_ASSERT(NGHTTP2_INITIAL_WINDOW_SIZE + 950 ==
+            nghttp2_session_get_stream_effective_local_window_size
+            (session, 1));
+  CU_ASSERT(0 == nghttp2_session_get_stream_effective_recv_data_length
+            (session, 1));
+
+  stream->recv_window_size += 50;
+  /* Now stream->recv_window_size = 0 */
+  nghttp2_submit_window_update(session, NGHTTP2_FLAG_NONE, 1, 100);
+  CU_ASSERT(NGHTTP2_INITIAL_WINDOW_SIZE + 1050 ==
+            nghttp2_session_get_stream_effective_local_window_size
+            (session, 1));
+  CU_ASSERT(50 ==
+            nghttp2_session_get_stream_effective_recv_data_length
+            (session, 1));
+}
+
 void test_nghttp2_session_set_option(void)
 {
   nghttp2_session* session;
diff --git a/tests/nghttp2_session_test.h b/tests/nghttp2_session_test.h
index 1cac4884..796cd071 100644
--- a/tests/nghttp2_session_test.h
+++ b/tests/nghttp2_session_test.h
@@ -87,6 +87,7 @@ void test_nghttp2_session_on_request_recv_callback(void);
 void test_nghttp2_session_on_stream_close(void);
 void test_nghttp2_session_on_ctrl_not_send(void);
 void test_nghttp2_session_get_outbound_queue_size(void);
+void test_nghttp2_session_get_effective_local_window_size(void);
 void test_nghttp2_session_set_option(void);
 void test_nghttp2_session_data_backoff_by_high_pri_frame(void);
 void test_nghttp2_pack_settings_payload(void);