diff --git a/apps/transport/mix.exs b/apps/transport/mix.exs
index deb08b502f..2a414e8d7a 100644
--- a/apps/transport/mix.exs
+++ b/apps/transport/mix.exs
@@ -76,6 +76,8 @@ defmodule Transport.Mixfile do
       {:cors_plug, "~> 2.0"},
       {:exvcr, "~> 0.10", only: :test},
       {:credo, "~> 1.0.0", only: [:dev, :test], runtime: false},
+      # NOTE: we cannot upgrade to the very latest (2.2.x) because of
+      # https://github.com/parroty/exvcr/issues/153#issuecomment-874864317
       {:ex_aws, "~> 2.1"},
       {:ex_aws_s3, "~> 2.0"},
       {:unidecode, "~> 1.0.0"},