diff --git a/include/osg/CullSettings b/include/osg/CullSettings
index 8da99af6e..bf06fbfc7 100644
--- a/include/osg/CullSettings
+++ b/include/osg/CullSettings
@@ -165,8 +165,8 @@ class SG_EXPORT CullSettings
           * can target either Matrix data type, configured at compile time.*/
         struct ClampProjectionMatrixCallback : public osg::Referenced
         {
-            virtual bool clampProjectionMatrixImplementation(osg::Matrixf& projection, double znear, double zfar) const = 0;
-            virtual bool clampProjectionMatrixImplementation(osg::Matrixd& projection, double znear, double zfar) const = 0;
+            virtual bool clampProjectionMatrixImplementation(osg::Matrixf& projection, double& znear, double& zfar) const = 0;
+            virtual bool clampProjectionMatrixImplementation(osg::Matrixd& projection, double& znear, double& zfar) const = 0;
         };
         
         /** set the ClampProjectionMatrixCallback.*/
diff --git a/include/osgUtil/CullVisitor b/include/osgUtil/CullVisitor
index e4eec873a..c36d73847 100644
--- a/include/osgUtil/CullVisitor
+++ b/include/osgUtil/CullVisitor
@@ -205,7 +205,7 @@ class OSGUTIL_EXPORT CullVisitor : public osg::NodeVisitor, public osg::CullStac
         }
 
         /** clamp the projection double matrix to computed near and far values, use callback if it exists, otherwise use default CullVisitro implemntation.*/
-        inline bool clampProjectionMatrix(osg::Matrixd& projection, value_type znear, value_type zfar) const
+        inline bool clampProjectionMatrix(osg::Matrixd& projection, value_type& znear, value_type& zfar) const
         {
             double zn = znear;
             double zf = zfar;
diff --git a/src/osgUtil/CullVisitor.cpp b/src/osgUtil/CullVisitor.cpp
index 0e8801b91..dfd8d6a46 100644
--- a/src/osgUtil/CullVisitor.cpp
+++ b/src/osgUtil/CullVisitor.cpp
@@ -211,13 +211,7 @@ void CullVisitor::popProjectionMatrix()
         // so it doesn't cull them out.
         osg::Matrix& projection = *_projectionStack.back();
         
-        double znear = _computed_znear;
-        double zfar = _computed_zfar;
-
-        clampProjectionMatrix(projection, znear, zfar);
-        
-        _computed_znear = znear;
-        _computed_zfar = zfar;
+        clampProjectionMatrix(projection, _computed_znear, _computed_zfar);
     }
     else
     {