diff --git a/lib/transports/polling-xhr.js b/lib/transports/polling-xhr.js
index 297bac59e..6044266a9 100755
--- a/lib/transports/polling-xhr.js
+++ b/lib/transports/polling-xhr.js
@@ -239,13 +239,12 @@ Request.prototype.create = function () {
     } else {
       xhr.onreadystatechange = function () {
         if (xhr.readyState === 2) {
-          var contentType;
           try {
-            contentType = xhr.getResponseHeader('Content-Type');
+            var contentType = xhr.getResponseHeader('Content-Type');
+            if (contentType === 'application/octet-stream') {
+              xhr.responseType = 'arraybuffer';
+            }
           } catch (e) {}
-          if (contentType === 'application/octet-stream') {
-            xhr.responseType = 'arraybuffer';
-          }
         }
         if (4 !== xhr.readyState) return;
         if (200 === xhr.status || 1223 === xhr.status) {