--- a/jaxws/src/java.xml.ws/share/classes/com/sun/xml/internal/ws/binding/SOAPBindingImpl.java	Fri Feb 10 00:39:51 2017 -0800
+++ b/jaxws/src/java.xml.ws/share/classes/com/sun/xml/internal/ws/binding/SOAPBindingImpl.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
@@ -42,6 +42,8 @@
 import javax.xml.ws.soap.MTOMFeature;
 import javax.xml.ws.soap.SOAPBinding;
 import java.util.*;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 /**
  * @author WS Development Team
@@ -57,6 +59,7 @@
 
     private Set<QName> portKnownHeaders = Collections.emptySet();
     private Set<QName> bindingUnderstoodHeaders = new HashSet<QName>();
+    private final Lock lock = new ReentrantLock();
 
     /**
      * Use {@link BindingImpl#create(BindingID)} to create this.
@@ -95,7 +98,13 @@
      * @param headers SOAP header names
      */
     public void setPortKnownHeaders(@NotNull Set<QName> headers) {
-        this.portKnownHeaders = headers;
+
+        try{
+          lock.lock();
+          this.portKnownHeaders = headers;
+                } finally {
+                lock.unlock();
+        }
     }
 
     /**