diff --git a/Triangulation_3/include/CGAL/Constrained_Delaunay_triangulation_3.h b/Triangulation_3/include/CGAL/Constrained_Delaunay_triangulation_3.h
index d7a17db7f13..bbb805c54a9 100644
--- a/Triangulation_3/include/CGAL/Constrained_Delaunay_triangulation_3.h
+++ b/Triangulation_3/include/CGAL/Constrained_Delaunay_triangulation_3.h
@@ -1956,16 +1956,22 @@ public:
     switch(this->dimension()) {
     case 3: {
       for(auto it = this->finite_cells_begin(), end = this->finite_cells_end(); it != end; ++it) {
-        this->is_valid_finite(it);
+        this->is_valid_finite(it, verbose, level);
         for(int i = 0; i < 4; i++) {
           const auto n = it->neighbor(i);
           const auto n_index = n->index(it);
           if(!this->is_infinite(n->vertex(n_index)))
           {
             if(!it->is_facet_constrained(i) && this->side_of_sphere(it, n->vertex(n_index)->point()) == ON_BOUNDED_SIDE) {
-              if(verbose)
-                std::cerr << "non-empty sphere " << std::endl;
-
+              if(verbose) {
+                std::cerr << "non-empty sphere at non-constrainted facet (" << IO::oformat(Cell_handle(it))
+                          << ", " << i << ") the cell is:\n  "
+                          << IO::oformat(it->vertex(0), with_point) << "\n  "
+                          << IO::oformat(it->vertex(1), with_point) << "\n  "
+                          << IO::oformat(it->vertex(2), with_point) << "\n  "
+                          << IO::oformat(it->vertex(3), with_point) << "\ncontains:\n  "
+                          << IO::oformat(n->vertex(n_index), with_point_and_info) << '\n';
+              }
               CGAL_assertion(false);
               return false;
             }
@@ -1977,7 +1983,7 @@ public:
     case 2: {
       for(auto it = this->finite_facets_begin(), end = this->finite_facets_end(); it != end; ++it) {
         const auto c = it->first;
-        this->is_valid_finite(c);
+        this->is_valid_finite(c, verbose, level);
         for(int i = 0; i < 3; i++) {
           const auto n = c->neighbor(i);
           const auto n_index = n->index(c);
@@ -1996,7 +2002,7 @@ public:
     }
     case 1: {
       for(auto it = this->finite_edges_begin(), end = this->finite_edges_end(); it != end; ++it) {
-        this->is_valid_finite((*it).first);
+        this->is_valid_finite((*it).first, verbose, level);
       }
       break;
     }