diff --git a/lib/includes/spdylay/spdylay.h b/lib/includes/spdylay/spdylay.h
index d1c54443..0329775b 100644
--- a/lib/includes/spdylay/spdylay.h
+++ b/lib/includes/spdylay/spdylay.h
@@ -1894,15 +1894,16 @@ int spdylay_submit_settings(spdylay_session *session, uint8_t flags,
 /**
  * @function
  *
- * Submits WINDOW_UPDATE frame. The library keeps track of the
- * received bytes from the remote endpoint. If the |delta_window_size|
- * is larger than the received bytes, then it is reduced to the
- * received bytes. If the received bytes is 0, the library will not
- * send this frame.
+ * Submits WINDOW_UPDATE frame. The effective range of the
+ * |delta_window_size| is [1, (1 << 31)-1], inclusive. But the
+ * application must be responsible to keep the resulting window size
+ * <= (1 << 31)-1.
  *
  * This function returns 0 if it succeeds, or one of the following
  * negative error codes:
  *
+ * :enum:`SPDYLAY_ERR_INVALID_ARGUMENT`
+ *     The |delta_window_size| is 0 or negative.
  * :enum:`SPDYLAY_ERR_STREAM_CLOSED`
  *     The stream is already closed or does not exist.
  * :enum:`SPDYLAY_ERR_NOMEM`
diff --git a/lib/spdylay_submit.c b/lib/spdylay_submit.c
index 730d48ca..488205ac 100644
--- a/lib/spdylay_submit.c
+++ b/lib/spdylay_submit.c
@@ -233,16 +233,15 @@ int spdylay_submit_window_update(spdylay_session *session, int32_t stream_id,
                                  int32_t delta_window_size)
 {
   spdylay_stream *stream;
+  if(delta_window_size <= 0) {
+    return SPDYLAY_ERR_INVALID_ARGUMENT;
+  }
   stream = spdylay_session_get_stream(session, stream_id);
   if(stream) {
-    delta_window_size = spdylay_min(delta_window_size,
-                                    stream->recv_window_size);
-    if(delta_window_size > 0) {
-      stream->recv_window_size -= delta_window_size;
-      return spdylay_session_add_window_update(session, stream_id,
-                                               delta_window_size);
-    }
-    return 0;
+    stream->recv_window_size -= spdylay_min(delta_window_size,
+                                            stream->recv_window_size);
+    return spdylay_session_add_window_update(session, stream_id,
+                                             delta_window_size);
   } else {
     return SPDYLAY_ERR_STREAM_CLOSED;
   }
diff --git a/tests/spdylay_session_test.c b/tests/spdylay_session_test.c
index 0fcbf231..5b7588bb 100644
--- a/tests/spdylay_session_test.c
+++ b/tests/spdylay_session_test.c
@@ -2339,15 +2339,27 @@ void test_spdylay_submit_window_update(void)
   CU_ASSERT(SPDYLAY_WINDOW_UPDATE == OB_CTRL_TYPE(item));
   CU_ASSERT(1024 == OB_CTRL(item)->window_update.delta_window_size);
   CU_ASSERT(0 == spdylay_session_send(session));
+  CU_ASSERT(3072 == stream->recv_window_size);
 
   CU_ASSERT(0 == spdylay_submit_window_update(session, stream_id, 4096));
   item = spdylay_session_get_next_ob_item(session);
   CU_ASSERT(SPDYLAY_WINDOW_UPDATE == OB_CTRL_TYPE(item));
-  CU_ASSERT(3072 == OB_CTRL(item)->window_update.delta_window_size);
+  CU_ASSERT(4096 == OB_CTRL(item)->window_update.delta_window_size);
   CU_ASSERT(0 == spdylay_session_send(session));
+  CU_ASSERT(0 == stream->recv_window_size);
 
   CU_ASSERT(0 == spdylay_submit_window_update(session, stream_id, 4096));
-  CU_ASSERT(NULL == spdylay_session_get_next_ob_item(session));
+  CU_ASSERT(SPDYLAY_WINDOW_UPDATE == OB_CTRL_TYPE(item));
+  CU_ASSERT(4096 == OB_CTRL(item)->window_update.delta_window_size);
+  CU_ASSERT(0 == spdylay_session_send(session));
+  CU_ASSERT(0 == stream->recv_window_size);
+
+  CU_ASSERT(SPDYLAY_ERR_INVALID_ARGUMENT ==
+            spdylay_submit_window_update(session, stream_id, 0));
+  CU_ASSERT(SPDYLAY_ERR_INVALID_ARGUMENT ==
+            spdylay_submit_window_update(session, stream_id, -1));
+  CU_ASSERT(SPDYLAY_ERR_STREAM_CLOSED ==
+            spdylay_submit_window_update(session, 4, 4096));
 
   spdylay_session_del(session);
 }