diff --git a/lib/sync.js b/lib/sync.js
index 95d07e281..6b4a78d92 100644
--- a/lib/sync.js
+++ b/lib/sync.js
@@ -428,7 +428,7 @@ SyncApi.prototype._sync = function(syncOptions, attempt) {
         // - The isBrandNewRoom boilerplate is boilerplatey.
 
         try {
-            self._processSyncResponse(data);
+            self._processSyncResponse(syncToken, data);
         }
         catch (e) {
             console.error("Caught /sync error:");
@@ -481,9 +481,11 @@ SyncApi.prototype._sync = function(syncOptions, attempt) {
  * Process data returned from a sync response and propagate it
  * into the model objects
  *
+ * @param {string} syncToken the old next_batch token sent to this
+ *    sync request.
  * @param {Object} data The response from /sync
  */
-SyncApi.prototype._processSyncResponse = function(data) {
+SyncApi.prototype._processSyncResponse = function(syncToken, data) {
     var client = this.client;
     var self = this;