diff --git a/Modules/Filtering/Contrast/include/otbComputeGainLutFilter.h b/Modules/Filtering/Contrast/include/otbComputeGainLutFilter.h
index ef623e08b58f5b25e95f88e5c978b1ed51ff9287..431b6f1f0f5f55d0bc5c403a1df86e8f5f26e255 100644
--- a/Modules/Filtering/Contrast/include/otbComputeGainLutFilter.h
+++ b/Modules/Filtering/Contrast/include/otbComputeGainLutFilter.h
@@ -114,7 +114,7 @@ private:
   double m_Max;
   double m_Step;
   unsigned int m_NbBin;
-  long m_NbPixel;
+  unsigned long m_NbPixel;
 
 };