diff --git a/zesje/pregrader.py b/zesje/pregrader.py
index 269c81be83c9f7b35f6c671a1a62ecfc2ddcdf3e..71b946e05a3c77ae3f85930a9401fd7da64d2d83 100644
--- a/zesje/pregrader.py
+++ b/zesje/pregrader.py
@@ -34,7 +34,7 @@ def add_feedback_to_solution(page, page_img, corner_keypoints):
 
             box = (mc_option.x, mc_option.y)
 
-            corner_keypoints = fix_corner_markers(corner_keypoints, image=page_img, image_format=1)
+            corner_keypoints = fix_corner_markers(corner_keypoints, page_img.shape)
 
             # check if box is filled
             if box_is_filled(box, page_img, corner_keypoints):