diff --git a/AABB_tree/include/CGAL/AABB_traits_3.h b/AABB_tree/include/CGAL/AABB_traits_3.h
index 30a3fa77cd3..9342e69aa13 100644
--- a/AABB_tree/include/CGAL/AABB_traits_3.h
+++ b/AABB_tree/include/CGAL/AABB_traits_3.h
@@ -302,12 +302,11 @@ public:
     typename AT::Bounding_box operator()(ConstPrimitiveIterator first,
                                          ConstPrimitiveIterator beyond) const
     {
-      typename AT::Bounding_box bbox = m_traits.compute_bbox(*first,m_traits.bbm);
-      for(++first; first != beyond; ++first)
-        {
-          bbox = bbox + m_traits.compute_bbox(*first,m_traits.bbm);
-        }
-      return bbox;
+      return std::accumulate(first, beyond,
+        typename AT::Bounding_box{} /* empty bbox */,
+        [this](const typename AT::Bounding_box& bbox, const Primitive& pr) {
+          return bbox + m_traits.compute_bbox(pr, m_traits.bbm);
+        });
     }
 
   };
diff --git a/AABB_tree/include/CGAL/AABB_tree.h b/AABB_tree/include/CGAL/AABB_tree.h
index 9dd8460abd2..fdc6a71817c 100644
--- a/AABB_tree/include/CGAL/AABB_tree.h
+++ b/AABB_tree/include/CGAL/AABB_tree.h
@@ -199,9 +199,7 @@ namespace CGAL {
     }
 
     /// returns the axis-aligned bounding box of the whole tree.
-    /// \pre `!empty()`
     const Bounding_box bbox() const {
-      CGAL_precondition(!empty());
       if(size() > 1)
         return root_node()->bbox();
       else