diff --git a/ccv/sheet4/lab_pyramid.cpp b/ccv/sheet4/lab_pyramid.cpp
index 74d4444..c21e384 100644
--- a/ccv/sheet4/lab_pyramid.cpp
+++ b/ccv/sheet4/lab_pyramid.cpp
@@ -66,8 +66,8 @@ void lab_pyramid::compute_dog(lab_pyramid center, lab_pyramid surround, int numb
     cv::Mat dog_final_sc_L;
     cv::threshold(dog_raw_cs_L, dog_final_cs_L, 0, 1, cv::THRESH_TOZERO);
     _cs_contrast_l.push_back(dog_final_cs_L);
-    cv::Mat dog_raw_sc = surround_layer_mat_L - center_layer_mat_L;
-    cv::threshold(dog_raw_sc, dog_final_sc_L, 0, 1, cv::THRESH_TOZERO);
+    cv::Mat dog_raw_sc_L = surround_layer_mat_L - center_layer_mat_L;
+    cv::threshold(dog_raw_sc_L, dog_final_sc_L, 0, 1, cv::THRESH_TOZERO);
     _sc_contrast_l.push_back(dog_final_sc_L);
 
     // A channel
@@ -91,7 +91,7 @@ void lab_pyramid::compute_dog(lab_pyramid center, lab_pyramid surround, int numb
     cv::threshold(dog_raw_cs_b, dog_final_cs_b, 0, 1, cv::THRESH_TOZERO);
     _cs_contrast_b.push_back(dog_final_cs_b);
     cv::Mat dog_raw_sc_b = surround_layer_mat_b - center_layer_mat_b;
-    cv::threshold(dog_raw_cs_b, dog_final_sc_b, 0, 1, cv::THRESH_TOZERO);
+    cv::threshold(dog_raw_sc_b, dog_final_sc_b, 0, 1, cv::THRESH_TOZERO);
     _sc_contrast_b.push_back(dog_final_sc_b);
   }
 }