Index: api/src/main/java/org/apache/cxf/endpoint/ClientCallback.java
===================================================================
--- api/src/main/java/org/apache/cxf/endpoint/ClientCallback.java    (revisione 12700)
+++ api/src/main/java/org/apache/cxf/endpoint/ClientCallback.java    (copia locale)
@@ -35,7 +35,7 @@
    protected Map<String, Object> context;
    protected Object[] result;
    protected Throwable exception;
-    protected boolean done;
+    protected volatile boolean done;
    protected boolean cancelled;
    protected boolean started;