diff --git a/applications/dyndns/index.js b/applications/dyndns/index.js
index ff7b26a..e08e029 100644
--- a/applications/dyndns/index.js
+++ b/applications/dyndns/index.js
@@ -263,6 +263,10 @@ async function init () {
       res.send('Nothing to do')
     }
 
+    // Remove subnet masks
+    if (v6) v6 = v6.replace(/\/(\d+)$/, '')
+    if (v4) v4 = v4.replace(/\/(\d+)$/, '')
+
     try {
       await updateZone(Object.assign({
         token: token,