diff --git a/src/osgViewer/Viewer.cpp b/src/osgViewer/Viewer.cpp
index 2e7f9a7f5..5eca20b25 100644
--- a/src/osgViewer/Viewer.cpp
+++ b/src/osgViewer/Viewer.cpp
@@ -706,7 +706,7 @@ void Viewer::setThreadingModel(ThreadingModel threadingModel)
     
     _threadingModel = threadingModel;
 
-    if (_threadingModel!=SingleThreaded) startThreading();
+    if (isRealized() && _threadingModel!=SingleThreaded) startThreading();
 }
 
 void Viewer::setUpThreading()