diff --git a/Lab/demo/Lab/Scene_c3t3_item.cpp b/Lab/demo/Lab/Scene_c3t3_item.cpp
index 7e1999643ea..4c59b8a513a 100644
--- a/Lab/demo/Lab/Scene_c3t3_item.cpp
+++ b/Lab/demo/Lab/Scene_c3t3_item.cpp
@@ -355,6 +355,7 @@ void Scene_c3t3_item::reset_surface_patches()
     f.first->set_surface_patch_index(f.second, first_index);
     mf.first->set_surface_patch_index(mf.second, first_index);
   }
+  triangulation_changed();
   this->invalidateOpenGLBuffers();
   Q_EMIT itemChanged();
 }
diff --git a/Lab/demo/Lab/Scene_triangulation_3_item.cpp b/Lab/demo/Lab/Scene_triangulation_3_item.cpp
index 1fdbe92d2cb..629b5be9115 100644
--- a/Lab/demo/Lab/Scene_triangulation_3_item.cpp
+++ b/Lab/demo/Lab/Scene_triangulation_3_item.cpp
@@ -727,9 +727,11 @@ Scene_triangulation_3_item::triangulation_changed()
   for (Tr::Finite_facets_iterator fit = triangulation().finite_facets_begin(),
        end = triangulation().finite_facets_end(); fit != end; ++fit)
   {
-    max = (std::max)(max, fit->first->surface_patch_index(fit->second));
-    int index = fit->first->surface_patch_index(fit->second);
-    d->surface_patch_indices_.insert(index);
+    const int index = fit->first->surface_patch_index(fit->second);
+    max = (std::max)(max, index);
+    if(index != 0)
+      d->surface_patch_indices_.insert(index);
+
     int dom0 = fit->first->subdomain_index();
     int dom1 = fit->first->neighbor(fit->second)->subdomain_index();
     if (dom0 == 0) // if cell is not in complex