diff --git a/EyeRecToo/src/pupil-detection/PuRe.cpp b/EyeRecToo/src/pupil-detection/PuRe.cpp
index f8f4ebf33c25f6374a2bc9da622cde4f4b44138c..9c4a1e6b1e26d1c66905fc795f1533564ea8d620 100644
--- a/EyeRecToo/src/pupil-detection/PuRe.cpp
+++ b/EyeRecToo/src/pupil-detection/PuRe.cpp
@@ -142,8 +142,8 @@ Mat PuRe::canny(const Mat& in, const bool blurImage, const bool useL2, const int
     } else
         blurred = in;
 
-    Sobel(blurred, dx, dx.type(), 1, 0, 7, 1, BORDER_REPLICATE);
-    Sobel(blurred, dy, dy.type(), 0, 1, 7, 1, BORDER_REPLICATE);
+    Sobel(blurred, dx, dx.type(), 1, 0, 7, 1, 0, BORDER_REPLICATE);
+    Sobel(blurred, dy, dy.type(), 0, 1, 7, 1, 0, BORDER_REPLICATE);
 
     /*
 	 *  Magnitude