diff --git a/include/vde/curves/nurbs_curve.h b/include/vde/curves/nurbs_curve.h
index bb65601..21a7978 100644
--- a/include/vde/curves/nurbs_curve.h
+++ b/include/vde/curves/nurbs_curve.h
@@ -38,6 +38,7 @@ public:
      *                {1, sqrt2/2, 1, sqrt2/2, 1, sqrt2/2, 1}, 3);
      * @endcode
      */
+    NurbsCurve() : degree_(0) {}  // degenerate empty curve
     NurbsCurve(std::vector<Point3D> control_points, std::vector<double> knots,
                std::vector<double> weights, int degree);
 
diff --git a/include/vde/curves/nurbs_surface.h b/include/vde/curves/nurbs_surface.h
index b331600..53b1e8b 100644
--- a/include/vde/curves/nurbs_surface.h
+++ b/include/vde/curves/nurbs_surface.h
@@ -35,6 +35,7 @@ public:
      * NurbsSurface sphere(grid, u_knots, v_knots, weights, 3, 3);
      * @endcode
      */
+    NurbsSurface() : degree_u_(0), degree_v_(0) {}  // degenerate empty surface
     NurbsSurface(std::vector<std::vector<Point3D>> control_grid,
                  std::vector<double> knots_u, std::vector<double> knots_v,
                  std::vector<std::vector<double>> weights,