diff --git a/ccv/saliency/gauss_pyramid.cpp b/ccv/saliency/gauss_pyramid.cpp
index 0311fe0..2aaca22 100644
--- a/ccv/saliency/gauss_pyramid.cpp
+++ b/ccv/saliency/gauss_pyramid.cpp
@@ -2,7 +2,7 @@
 
 gauss_pyramid::gauss_pyramid() {}
 
-gauss_pyramid::gauss_pyramid(cv::Mat img, float sigma, int number_of_layers)
+gauss_pyramid::gauss_pyramid(const cv::Mat img, float sigma, int number_of_layers)
 {
   cv::Mat blurredImage;
   cv::Mat resizedImage = img.clone();
diff --git a/ccv/saliency/includes/gauss_pyramid.h b/ccv/saliency/includes/gauss_pyramid.h
index 7a54d26..844f791 100644
--- a/ccv/saliency/includes/gauss_pyramid.h
+++ b/ccv/saliency/includes/gauss_pyramid.h
@@ -9,7 +9,7 @@ private:
     std::vector<cv::Mat> _layers;
 public:
     gauss_pyramid();
-    gauss_pyramid(cv::Mat img, float sigma, int number_of_layers);
+    gauss_pyramid(const cv::Mat img, float sigma, int number_of_layers);
     cv::Mat get(int layer) const;
     cv::Mat get(int layer);
     unsigned long get_number_of_layers() const;