diff --git a/include/itkMetamorphosisImageRegistrationMethodv4.h b/include/itkMetamorphosisImageRegistrationMethodv4.h
index 9cafb9c..83115d0 100644
--- a/include/itkMetamorphosisImageRegistrationMethodv4.h
+++ b/include/itkMetamorphosisImageRegistrationMethodv4.h
@@ -206,7 +206,7 @@ public TimeVaryingVelocityFieldImageRegistrationMethodv4<TFixedImage, TMovingIma
 
   double GetVelocityEnergy();
   double GetRateEnergy();
-  double GetImageEnergy(VirtualImagePointer movingImage, MaskPointer movingMask=ITK_NULLPTR);
+  double GetImageEnergy(VirtualImagePointer movingImage, MaskPointer movingMask=nullptr);
   double GetImageEnergy();
   double GetImageEnergyFraction();
   double GetEnergy();
diff --git a/include/itkWrapExtrapolateImageFunction.h b/include/itkWrapExtrapolateImageFunction.h
index ac17c5a..67dcf33 100644
--- a/include/itkWrapExtrapolateImageFunction.h
+++ b/include/itkWrapExtrapolateImageFunction.h
@@ -118,7 +118,7 @@ class WrapExtrapolateImageFunction:
   void SetInterpolator(InterpolatorType* ptr)
   {
     m_Interpolator = dynamic_cast<InterpolatorType*>(ptr);
-    if(ptr != ITK_NULLPTR)
+    if(ptr != nullptr)
     {
       m_Interpolator->SetInputImage(this->GetInputImage());
     }