diff --git a/lib/defaults.js b/lib/defaults.js
index cb061af4c0..b62f1e962a 100644
--- a/lib/defaults.js
+++ b/lib/defaults.js
@@ -77,7 +77,7 @@ var defaults = {
     var contentType = headers && headers['Content-Type'];
 
     if ( isObjectPayload && contentType === 'multipart/form-data' ) {
-      return toFormData(data,  new (this.env && this.env.FormData || FormData));
+      return toFormData(data,  this.env && this.env.FormData);
     } else if ( isObjectPayload || contentType === 'application/json' ) {
       setContentTypeIfUnset(headers, 'application/json');
       return stringifySafely(data);
diff --git a/lib/helpers/toFormData.js b/lib/helpers/toFormData.js
index 0f03b79861..3a683f8a6e 100644
--- a/lib/helpers/toFormData.js
+++ b/lib/helpers/toFormData.js
@@ -46,12 +46,11 @@ function buildFormData(formData, data, parentKey) {
  * type FormVal = FormDataNest | FormDataPrimitive
  *
  * @param {FormVal} data
- * @param {?Object} formData
+ * @param {?Class} EnvFormData
  */
 
-module.exports = function getFormData(data, formData) {
-  // eslint-disable-next-line no-param-reassign
-  formData = formData || new FormData();
+module.exports = function getFormData(data, EnvFormData) {
+  var formData = new (EnvFormData || FormData)();
 
   buildFormData(formData, data);