diff --git a/docs/client.rst b/docs/client.rst
index 997e8a3b..4186109c 100644
--- a/docs/client.rst
+++ b/docs/client.rst
@@ -6,6 +6,12 @@ the imports::
 
     from flask_oauthlib.client import OAuth
 
+.. attention:: If you are testing the provider and the client locally, do not
+   start they listening on the same address because they will
+   override the `session` of each other leading to strange bugs.
+   eg: start the provider listening on `127.0.0.1:4000` and client
+   listening on `localhost:4000` to avoid this problem.
+
 .. _`Flask-OAuth`: http://pythonhosted.org/Flask-OAuth/