diff --git a/lib/adapters/xhr.js b/lib/adapters/xhr.js
index c930f2e..5432cce 100644
--- a/lib/adapters/xhr.js
+++ b/lib/adapters/xhr.js
@@ -125,6 +125,11 @@ module.exports = function xhrAdapter(resolve, reject, config) {
     requestData = new DataView(requestData);
   }
 
+  // Clean up request
+  requestData = (requestData === undefined)
+                ? null
+                : requestData;
+
   // Send the request
   request.send(requestData);
 };