diff --git a/aos/vision/blob/contour.h b/aos/vision/blob/contour.h
index 9cd1400..bbd59a9 100644
--- a/aos/vision/blob/contour.h
+++ b/aos/vision/blob/contour.h
@@ -25,6 +25,7 @@
   ContourNode *pappend(int x, int y, AnalysisAllocator *alloc) {
     return alloc->cons_obj<ContourNode>(x, y, this);
   }
+  void set_point(Point new_pt) { pt = new_pt; }
 
   Point pt;
   ContourNode *next;