diff --git a/src/osgVolume/MultipassTechnique.cpp b/src/osgVolume/MultipassTechnique.cpp
index e0e7ab538..3fb79cafe 100644
--- a/src/osgVolume/MultipassTechnique.cpp
+++ b/src/osgVolume/MultipassTechnique.cpp
@@ -928,33 +928,6 @@ void MultipassTechnique::backfaceSubgraphCullTraversal(osgUtil::CullVisitor* cv)
     cv->popStateSet();
 }
 
-class RTTBackfaceCameraCullCallback : public osg::NodeCallback
-{
-    public:
-
-        RTTBackfaceCameraCullCallback(MultipassTechnique::MultipassTileData* tileData, MultipassTechnique* mt):
-            _tileData(tileData),
-            _mt(mt) {}
-
-        virtual void operator()(osg::Node* /*node*/, osg::NodeVisitor* nv)
-        {
-            osgUtil::CullVisitor* cv = nv->asCullVisitor();
-
-            cv->pushProjectionMatrix(_tileData->projectionMatrix.get());
-
-            _mt->backfaceSubgraphCullTraversal(cv);
-
-            cv->popProjectionMatrix();
-        }
-
-    protected:
-
-        virtual ~RTTBackfaceCameraCullCallback() {}
-
-        osg::observer_ptr<osgVolume::MultipassTechnique::MultipassTileData> _tileData;
-        osg::observer_ptr<osgVolume::MultipassTechnique> _mt;
-};
-
 class ShadingModelVisitor : public osgVolume::PropertyVisitor
 {
     public: