diff --git a/content/spaces/setup.textile b/content/spaces/setup.textile
index 3ba354489c..85c6af7617 100644
--- a/content/spaces/setup.textile
+++ b/content/spaces/setup.textile
@@ -55,6 +55,10 @@ Reference the Ably JavaScript SDK and the Spaces SDK within the @<head>@ of your
 <script src="https://cdn.ably.com/spaces/0.1.2/iife/index.bundle.js"></script>
 ```
 
+<aside data-type='note'>
+If you are using the CDN version of the Ably client, replace the call to `new Realtime.Promise` in the next section with `new Ably.Realtime.Promise`.
+</aside>
+
 h2(#instantiate). Instantiate
 
 Instantiate a realtime client using the Ably JavaScript SDK and pass the generated client into the Spaces constructor:
