diff --git a/synfig-studio/src/gui/vectorizer/polygonizerclasses.h b/synfig-studio/src/gui/vectorizer/polygonizerclasses.h
index 901f895..a4b3253 100644
--- a/synfig-studio/src/gui/vectorizer/polygonizerclasses.h
+++ b/synfig-studio/src/gui/vectorizer/polygonizerclasses.h
@@ -273,7 +273,7 @@ class SkeletonArc {
 public:
   SkeletonArc() : m_attributes(0) {}
   SkeletonArc(ContourNode *node)
-      : m_slope(node->m_direction.z)
+      : m_slope(node->m_direction[2])
       , m_leftGeneratingNode(node->m_ancestor)
       , m_leftContour(node->m_ancestorContour)
       , m_rightGeneratingNode(node->m_prev->m_ancestor)