diff --git a/lib/util.js b/lib/util.js
index 7f266a1..1b7ac30 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -245,7 +245,7 @@ module.exports = (function () {
       });
 
       response.on('end', function () {
-        if (contentType.indexOf('application/json') === -1) {
+        if (contentType != 'undefined' && contentType.indexOf('application/json') === -1) {
           callback(response.statusCode + ' API failed to return JSON content', null);
           return;
         }
@@ -278,4 +278,4 @@ module.exports = (function () {
 
   return util;
 
-})();
\ No newline at end of file
+})();