diff --git a/include/osgViewer/ViewerBase b/include/osgViewer/ViewerBase
index ac7ab2a75..4f631380e 100644
--- a/include/osgViewer/ViewerBase
+++ b/include/osgViewer/ViewerBase
@@ -111,7 +111,7 @@ class OSGVIEWER_EXPORT ViewerBase : public virtual osg::Object
          * or NO_OPERATION. NO_OPERATION is the default. Per BarrierOperation::operator()(),
          * a glFlush() command, glFinish() command, or no additional OpenGL command will be
          * issued before entering the end barrier. */
-        void setEndBarrierOperation(const osg::BarrierOperation::PreBlockOp& op) { _endBarrierOperation = op; }
+        void setEndBarrierOperation(osg::BarrierOperation::PreBlockOp op);
         
         /** Get the end barrier operation. */
         osg::BarrierOperation::PreBlockOp getEndBarrierOperation() const { return _endBarrierOperation; }
diff --git a/src/osgViewer/ViewerBase.cpp b/src/osgViewer/ViewerBase.cpp
index 1a96ebfab..b917afb00 100644
--- a/src/osgViewer/ViewerBase.cpp
+++ b/src/osgViewer/ViewerBase.cpp
@@ -179,6 +179,16 @@ void ViewerBase::setEndBarrierPosition(BarrierPosition bp)
     if (_threadingModel!=SingleThreaded) startThreading();
 }
 
+void ViewerBase::setEndBarrierOperation(osg::BarrierOperation::PreBlockOp op)
+{
+    if (_endBarrierOperation == op) return;
+
+    if (_threadsRunning) stopThreading();
+
+    _endBarrierOperation = op;
+
+    if (_threadingModel!=SingleThreaded) startThreading();
+}
 
 void ViewerBase::stopThreading()
 {