diff --git a/lib/nghttp2_hd.h b/lib/nghttp2_hd.h
index 21554b95..5cc11909 100644
--- a/lib/nghttp2_hd.h
+++ b/lib/nghttp2_hd.h
@@ -233,6 +233,8 @@ void nghttp2_hd_deflate_set_no_refset(nghttp2_hd_context *deflater,
  * Changes header table size in |context|. This may trigger eviction
  * in the dynamic table.
  *
+ * This function can be used for deflater and inflater.
+ *
  * This function returns 0 if it succeeds, or one of the following
  * negative error codes:
  *