diff --git a/lib/utils.js b/lib/utils.js
index a969bb6..60b127f 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -14,7 +14,7 @@ const determineTransport = function (transports, url) {
 }
 
 const negotiateDecoder = function (decoders, contentType) {
-  if (contentType === undefined) {
+  if (contentType === undefined || contentType === null) {
     return decoders[0]
   }