diff --git a/dnsconfig.js b/dnsconfig.js
index 833d3d6a58..faf5db4900 100644
--- a/dnsconfig.js
+++ b/dnsconfig.js
@@ -172,6 +172,32 @@ for (var subdomain in domains) {
     }
 }
 
+var existingSubdomains = new Set();
+var eligibleDomains = [];
+
+for (var i = 0; i < domains.length; i++) {
+    var subdomainName = domains[i].name;
+    var data = domains[i].data;
+
+    existingSubdomains.add(subdomainName);
+
+    if (
+        !subdomainName.startsWith("www.") &&
+        (data.records.A || data.records.AAAA || data.records.CNAME || data.records.URL)
+    ) {
+        eligibleDomains.push(subdomainName);
+    }
+}
+
+for (var i = 0; i < eligibleDomains.length; i++) {
+    var sub = eligibleDomains[i];
+    var wwwSub = "www." + sub;
+
+    if (!existingSubdomains.has(wwwSub)) {
+        records.push(A(wwwSub, IP("192.0.2.1"), CF_PROXY_ON));
+    }
+}
+
 var reserved = require("./util/reserved.json");
 
 // Handle reserved domains