diff --git a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Hole_filling/Triangulate_hole_polyline.h b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Hole_filling/Triangulate_hole_polyline.h
index f51ca3e861c..2c41228dc8a 100644
--- a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Hole_filling/Triangulate_hole_polyline.h
+++ b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Hole_filling/Triangulate_hole_polyline.h
@@ -1221,7 +1221,6 @@ bool is_planar_2(
   typedef typename Traits::FT FT;
   typedef typename Traits::Point_3 Point_3;
   typedef typename Traits::Plane_3 Plane_3;
-  typedef typename Traits::Vector_3 Vector_3;
   typedef typename Traits::Construct_projected_point_3 Projection_3;
   typedef typename Traits::Compute_squared_distance_3 Squared_distance_3;
 
@@ -1264,7 +1263,7 @@ bool is_planar_2(
   }
 
   // Here, avg_squared_distance is a little bit more tolerant than avg_distance^2.
-  CGAL_assertion(avg_normal != Vector_3());
+  CGAL_assertion(avg_normal != typename Traits::Vector_3());
   const Plane_3 plane = Plane_3(centroid, avg_normal);
   FT avg_squared_distance = FT(0);
   for (std::size_t i = 0; i < n; ++i) {