diff --git a/include/osgWidget/EventInterface b/include/osgWidget/EventInterface
index 2b67cac9b..ab5784d6e 100644
--- a/include/osgWidget/EventInterface
+++ b/include/osgWidget/EventInterface
@@ -161,6 +161,8 @@ struct CallbackInterface: public osg::Referenced
 {
     virtual ~CallbackInterface() {}
 
+    virtual const char* className() const { return "osgWidget::CallbackInterface"; }
+
     virtual bool operator()(Event&) = 0;
 };
 
@@ -207,6 +209,8 @@ class OSGWIDGET_EXPORT Callback: public osg::Referenced
         Callback(): _type(EVENT_NONE), _data(0), _callback(0) {}
         Callback(const Callback& rhs): osg::Referenced(rhs), _type(rhs._type), _data(rhs._data), _callback(rhs._callback) {}
 
+        virtual const char* className() const { return "osgWidget::Callback"; }
+
         // The more traditional style of OSG Callbacks.
         Callback(EventType type, void* data=0):
         _type     (type),