--- a/src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/ResponseSubscribers.java	Tue Dec 19 08:51:11 2017 -0800
+++ b/src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/ResponseSubscribers.java	Mon Dec 18 10:21:38 2017 +0000
@@ -62,7 +62,7 @@
         private final AtomicBoolean subscribed = new AtomicBoolean();
 
         ConsumerSubscriber(Consumer<Optional<byte[]>> consumer) {
-            this.consumer = consumer;
+            this.consumer = Objects.requireNonNull(consumer);
         }
 
         @Override