diff --git a/lib/stitches/api_key.rb b/lib/stitches/api_key.rb
index 04b2af8..9081c8a 100644
--- a/lib/stitches/api_key.rb
+++ b/lib/stitches/api_key.rb
@@ -57,6 +57,11 @@ def do_call(env)
 
   private
 
+    # TODO: (jdlubrano)
+    # Once Rails 5 support is no longer necessary, we can simply call
+    # Rails.application.class.module_parent.  The module_parent method
+    # does not exist in Rails <= 5, though, so we need to gracefully fallback
+    # Rails.application.class.parent for Rails versions predating Rails 6.0.0.
     def rails_app_module
       application_class = Rails.application.class
       parent = application_class.try(:module_parent) || application_class.parent