diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index a6048adc..75be754f 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -851,6 +851,10 @@ nghttp2_stream* nghttp2_session_open_stream(nghttp2_session *session,
     return stream;
   }
 
+  /* TODO Client does not have to track dependencies of streams except
+     for those which have upload data.  Currently, we just track
+     everything. */
+
   root_stream = nghttp2_stream_get_dep_root(dep_stream);
 
   if(root_stream->num_substreams < NGHTTP2_MAX_DEP_TREE_LENGTH) {
diff --git a/lib/nghttp2_session.h b/lib/nghttp2_session.h
index 45ab56ad..b398dc3b 100644
--- a/lib/nghttp2_session.h
+++ b/lib/nghttp2_session.h
@@ -132,10 +132,10 @@ struct nghttp2_session {
   int64_t next_seq;
   void *user_data;
   /* Points to the latest closed stream.  NULL if there is no closed
-     stream. */
+     stream.  Only used when session is initialized as server. */
   nghttp2_stream *closed_stream_head;
   /* Points to the oldest closed stream.  NULL if there is no closed
-     stream. */
+     stream.  Only used when session is initialized as server. */
   nghttp2_stream *closed_stream_tail;
   /* In-flight SETTINGS values. NULL does not necessarily mean there
      is no in-flight SETTINGS. */