diff --git a/docs/app.rst b/docs/app.rst
index 22f0ade8fda1958a7f02144a01cc6371074ce960..dbc260a610f92d6128a57b560221bd1c582572e6 100644
--- a/docs/app.rst
+++ b/docs/app.rst
@@ -30,7 +30,7 @@ Contents of `config.yml`::
     ssl_password: ''
     username: ''
     password: ''
-    response_timeout: None
+    response_timeout: null
     max_conns: 4
     min_conns: 1
     max_times_acquired: 16