diff --git a/jetty-client/src/main/java/org/eclipse/jetty/client/http/HttpReceiverOverHTTP.java b/jetty-client/src/main/java/org/eclipse/jetty/client/http/HttpReceiverOverHTTP.java
index 1a769d22ff7..7c4a1d348a9 100644
--- a/jetty-client/src/main/java/org/eclipse/jetty/client/http/HttpReceiverOverHTTP.java
+++ b/jetty-client/src/main/java/org/eclipse/jetty/client/http/HttpReceiverOverHTTP.java
@@ -94,7 +94,7 @@ public class HttpReceiverOverHTTP extends HttpReceiver implements HttpParser.Res
         if (BufferUtil.hasContent(buffer))
         {
             ByteBuffer upgradeBuffer = ByteBuffer.allocate(buffer.remaining());
-            upgradeBuffer.put(buffer);
+            upgradeBuffer.put(buffer).flip();
             return upgradeBuffer;
         }
         return null;