diff --git a/pvDataApp/monitor/monitor.h b/pvDataApp/monitor/monitor.h
index a5cf4eb..0ed7b68 100644
--- a/pvDataApp/monitor/monitor.h
+++ b/pvDataApp/monitor/monitor.h
@@ -69,7 +69,7 @@ namespace epics { namespace pvData {
      * Requester for ChannelMonitor.
      * @author mrk
      */
-    class MonitorRequester : public Requester {
+    class MonitorRequester : public virtual Requester {
         public:
         /**
          * The client and server have both completed the createMonitor request.