diff --git a/lib/objectList.js b/lib/objectList.js
index 501c0c5..b37674e 100644
--- a/lib/objectList.js
+++ b/lib/objectList.js
@@ -38,5 +38,7 @@ module.exports = [
   {name: 'Usage'},
   {name: 'BillingPreviewRequest'}, //BillingPreviewRequest
   {name: 'Request'},               //BillingPreviewRequest
-  {name: 'BillingPreviewRun', methods: ['create', 'query']}
+  {name: 'BillingPreviewRun', methods: ['create', 'query']},
+  {name: 'GenerateInvoice', methods: ['subscribe']},
+  {name: 'ProcessPayments', methods: ['subscribe']}
 ];
diff --git a/lib/xml.js b/lib/xml.js
index 9941f73..f00c1b4 100644
--- a/lib/xml.js
+++ b/lib/xml.js
@@ -73,7 +73,7 @@ var escapeFields = function(value) {
 };
 
 function convert (method, object, objectType) {
-  var zObjectMethods = ['create', 'update', 'generate'];
+  var zObjectMethods = ['create', 'update', 'generate', 'subscribe'];
   var ns1Actions = ['delete', 'execute'];
 
   var encapsulate = function(key, obj) {
@@ -124,6 +124,18 @@ function convert (method, object, objectType) {
           prefix = prefix || ns2;
           val = escapeFields(value);
         }
+        var subscribeFields = [
+          'Amount',
+          'EffectiveDate',
+          'ProcessPayments',
+          'GenerateInvoice',
+          'PaymentMethodId'
+        ];
+
+        if (method === 'subscribe' && subscribeFields.indexOf(key) >= 0) {
+          prefix = ns1;
+        }
+
         return tag(name, prefix, val, attributes);
       }
     }), '\n');