diff --git a/Nef_3/include/CGAL/Nef_3/Infimaximal_box.h b/Nef_3/include/CGAL/Nef_3/Infimaximal_box.h
index b1eb8d6b9ee..463b5f85f60 100644
--- a/Nef_3/include/CGAL/Nef_3/Infimaximal_box.h
+++ b/Nef_3/include/CGAL/Nef_3/Infimaximal_box.h
@@ -402,9 +402,9 @@ class Infimaximal_box<Tag_true, Kernel> {
     typename SNC_structure::Vertex_const_iterator v;
     CGAL_forall_vertices(v, snc) {
       Point_3 p(v->point());
-      if(p.hx()[0] > eval) eval = p.hx()[0];
-      if(p.hy()[0] > eval) eval = p.hy()[0];
-      if(p.hz()[0] > eval) eval = p.hz()[0];
+      if(abs(p.hx()[0]) > eval) eval = abs(p.hx()[0]);
+      if(abs(p.hy()[0]) > eval) eval = abs(p.hy()[0]);
+      if(abs(p.hz()[0]) > eval) eval = abs(p.hz()[0]);
     }
     eval *= 4;
     if(eval == 0) return 1;