diff --git a/content/graphql/subscriptions.md b/content/graphql/subscriptions.md
index f78e440525..f90122c4e4 100644
--- a/content/graphql/subscriptions.md
+++ b/content/graphql/subscriptions.md
@@ -86,6 +86,7 @@ Likewise with filters.
 ```typescript
 @Subscription('commentAdded', {
   filter(this: AuthorResolver, payload, variables) {
+    // "this" refers to an instance of "AuthorResolver" 
     return payload.commentAdded.repositoryName === variables.repoFullName;
   }
 })