diff --git a/Notes-about-GAE---Google-App-Engine.md b/Notes-about-GAE---Google-App-Engine.md
index b0fe5ae..d9bf9be 100644
--- a/Notes-about-GAE---Google-App-Engine.md
+++ b/Notes-about-GAE---Google-App-Engine.md
@@ -7,4 +7,5 @@ Make sure to add this block to `app.yaml` (see [1393](https://github.com/python-
 ```
 env_variables:
     GAE_USE_SOCKETS_HTTPLIB : 'true'
-```
\ No newline at end of file
+```
+Note: This environmental variable applies only to applications developed for the Standard Environment and using Python 2.7 (see (https://cloud.google.com/appengine/docs/standard/python/sockets/))
\ No newline at end of file