diff --git a/vtkutils/vtkRGBAColorTransferFunction.cxx b/vtkutils/vtkRGBAColorTransferFunction.cxx
index 604946315e2..2c3b79f858f 100644
--- a/vtkutils/vtkRGBAColorTransferFunction.cxx
+++ b/vtkutils/vtkRGBAColorTransferFunction.cxx
@@ -585,7 +585,11 @@ void vtkRGBAColorTransferFunction::AddHSVASegment(
 
 //------------------------------------------------------------------------------
 // Returns the RGBA color evaluated at the specified location
+#if VTK_MAJOR_VERSION > 7
+const unsigned char* vtkRGBAColorTransferFunction::MapValue(double x)
+#else
 unsigned char* vtkRGBAColorTransferFunction::MapValue(double x)
+#endif
 {
   double rgb[4];
   this->GetColor(x, rgb);
diff --git a/vtkutils/vtkRGBAColorTransferFunction.h b/vtkutils/vtkRGBAColorTransferFunction.h
index cba820b2a2d..6ddc38dc7a9 100644
--- a/vtkutils/vtkRGBAColorTransferFunction.h
+++ b/vtkutils/vtkRGBAColorTransferFunction.h
@@ -128,7 +128,11 @@ class VTKRENDERINGCORE_EXPORT vtkRGBAColorTransferFunction : public vtkScalarsTo
   /**
    * Map one value through the lookup table.
    */
+#if VTK_MAJOR_VERSION > 7
+  const unsigned char* MapValue(double v) override;
+#else
   unsigned char* MapValue(double v) override;
+#endif
 
   ///@{
   /**