diff --git a/src/ifcconvert/validation_utils.h b/src/ifcconvert/validation_utils.h
index eca3406563..382603371f 100644
--- a/src/ifcconvert/validation_utils.h
+++ b/src/ifcconvert/validation_utils.h
@@ -481,6 +481,11 @@ struct intersection_validator {
 				}
 
 				CGAL::Nef_polyhedron_3<Kernel_> nef = ifcopenshell::geometry::utils::create_nef_polyhedron(s);
+				if (nef.is_empty()) {
+					std::wcout << "Failed to create nef" << std::endl;
+					continue;
+				}
+
 				nef = CGAL::minkowski_sum_3(nef, cube);
 				std::wcout << "product: " << geom_object->product() << std::endl;
 				nefs.push_back({ geom_object->product(), nef });
diff --git a/src/ifcgeom/kernels/cgal/CgalKernel.cpp b/src/ifcgeom/kernels/cgal/CgalKernel.cpp
index 190a851470..3d6e76d9c8 100644
--- a/src/ifcgeom/kernels/cgal/CgalKernel.cpp
+++ b/src/ifcgeom/kernels/cgal/CgalKernel.cpp
@@ -94,7 +94,8 @@ CGAL::Nef_polyhedron_3<Kernel_> ifcopenshell::geometry::utils::create_nef_polyhe
 }
 
 CGAL::Nef_polyhedron_3<Kernel_> ifcopenshell::geometry::utils::create_nef_polyhedron(CGAL::Polyhedron_3<Kernel_> &polyhedron) {
-	if (polyhedron.is_valid()) {
+	if (polyhedron.is_valid() && polyhedron.is_closed()) {
+		// @todo is it necessary to triangulat?
 		CGAL::Polygon_mesh_processing::triangulate_faces(polyhedron);
 		CGAL::Nef_polyhedron_3<Kernel_> nef_polyhedron;
 		try {