diff --git a/src/osgViewer/CompositeViewer.cpp b/src/osgViewer/CompositeViewer.cpp
index 02c5e18bc..496b102a5 100644
--- a/src/osgViewer/CompositeViewer.cpp
+++ b/src/osgViewer/CompositeViewer.cpp
@@ -170,7 +170,7 @@ void CompositeViewer::setThreadingModel(ThreadingModel threadingModel)
     
     _threadingModel = threadingModel;
 
-    if (_threadingModel!=SingleThreaded) startThreading();
+    if (isRealized() && _threadingModel!=SingleThreaded) startThreading();
 }