diff --git a/Examples/Patented/SIFTDensityExample.cxx b/Examples/Patented/SIFTDensityExample.cxx
index d5859f8793fcc72155bc973ccd8add0625e7c733..5c2044b46c7ba285ce26af012e23783075a6d76d 100644
--- a/Examples/Patented/SIFTDensityExample.cxx
+++ b/Examples/Patented/SIFTDensityExample.cxx
@@ -21,6 +21,7 @@
 #include "otbImage.h"
 #include "otbImageFileReader.h"
 #include "otbImageFileWriter.h"
+#include "itkUnaryFunctorImageFilter.h"
 #include "itkRescaleIntensityImageFilter.h"
 
 //  Software Guide : BeginCommandLineArgs