src/java.desktop/unix/classes/sun/awt/X11/XMSelection.java

@@ -198,11 +198,11 @@
         XClientMessageEvent xce = xev.get_xclient();
         if (xce.get_message_type() == XA_MANAGER.getAtom()) {
             if (log.isLoggable(PlatformLogger.Level.FINE)) {
                 log.fine("client messags = " + xce);
             }
-            long timestamp = xce.get_data(0);
+            long timestamp = xce.get_data(0) & 0xFFFFFFFFL;
             long atom = xce.get_data(1);
             long owner = xce.get_data(2);
             long data = xce.get_data(3);
 
             XMSelection sel = getInstance(atom);