diff --git a/posts/2023-10-07-the-stack-part-2.md b/posts/2023-10-07-the-stack-part-2.md
index ccacebf..73238a3 100644
--- a/posts/2023-10-07-the-stack-part-2.md
+++ b/posts/2023-10-07-the-stack-part-2.md
@@ -206,9 +206,10 @@ export class Stack extends cdk.NestedStack {
       zoneName: props.domain,
     });
 
-    // Set up an ACM certificate for the domain, and validate it using DNS.
+    // Set up an ACM certificate for the domain + subdomains, and validate it using DNS.
     new acm.Certificate(this, "Certificate", {
       domainName: props.domain,
+      subjectAlternativeNames: [`*.${props.domain}`],
       validation: acm.CertificateValidation.fromDns(hostedZone),
     });
   }