diff --git a/lib/defaults.js b/lib/defaults.js
index c961426..7cb8a25 100644
--- a/lib/defaults.js
+++ b/lib/defaults.js
@@ -30,6 +30,7 @@ var defaults = {
   adapter: getDefaultAdapter(),
 
   transformRequest: [function transformRequest(data, headers) {
+    normalizeHeaderName(headers, 'Accept');
     normalizeHeaderName(headers, 'Content-Type');
     if (utils.isFormData(data) ||
       utils.isArrayBuffer(data) ||