diff --git a/src/main/java/io/socket/engineio/client/transports/PollingXHR.java b/src/main/java/io/socket/engineio/client/transports/PollingXHR.java
index ed118eb..827c24f 100644
--- a/src/main/java/io/socket/engineio/client/transports/PollingXHR.java
+++ b/src/main/java/io/socket/engineio/client/transports/PollingXHR.java
@@ -268,10 +268,10 @@ public class PollingXHR extends Polling {
 
         private void onLoad() {
             ResponseBody body = response.body();
-            String contentType = body.contentType().toString();
+            MediaType mediaType = body.contentType();
 
             try {
-                if (BINARY_CONTENT_TYPE.equalsIgnoreCase(contentType)) {
+                if (mediaType != null && BINARY_CONTENT_TYPE.equalsIgnoreCase(mediaType.toString())) {
                     this.onData(body.bytes());
                 } else {
                     this.onData(body.string());