--- a/jaxws/src/java.xml.ws/share/classes/com/sun/xml/internal/ws/binding/BindingImpl.java	Fri Feb 10 00:39:51 2017 -0800
+++ b/jaxws/src/java.xml.ws/share/classes/com/sun/xml/internal/ws/binding/BindingImpl.java	Thu Feb 16 13:14:39 2017 +0300
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -75,7 +75,7 @@
     //This is reset when ever Binding.setHandlerChain() or SOAPBinding.setRoles() is called.
     private HandlerConfiguration handlerConfig;
     private final Set<QName> addedHeaders = new HashSet<QName>();
-    private final Set<QName> knownHeaders = new HashSet<QName>();
+    private final Set<QName> knownHeaders = Collections.synchronizedSet(new HashSet<QName>());
     private final Set<QName> unmodKnownHeaders = Collections.unmodifiableSet(knownHeaders);
     private final BindingID bindingId;
     // Features that are set(enabled/disabled) on the binding