diff --git a/lib/new_relic/agent/instrumentation/notifications_subscriber.rb b/lib/new_relic/agent/instrumentation/notifications_subscriber.rb
index 1bff8b2732..09972206e5 100644
--- a/lib/new_relic/agent/instrumentation/notifications_subscriber.rb
+++ b/lib/new_relic/agent/instrumentation/notifications_subscriber.rb
@@ -47,6 +47,9 @@ def self.subscribe(pattern)
           end
         end
 
+        # The agent doesn't use the traditional ActiveSupport::Notifications.subscribe
+        # pattern due to threading issues discovered on initial instrumentation.
+        # Instead we define a #start and #finish method, which Rails responds to.
         def start(name, id, payload)
           return unless state.is_execution_traced?