diff --git a/HalfedgeDS/include/CGAL/boost/graph/graph_traits_HalfedgeDS.h b/HalfedgeDS/include/CGAL/boost/graph/graph_traits_HalfedgeDS.h
index 542d5a447f7..7413032092f 100644
--- a/HalfedgeDS/include/CGAL/boost/graph/graph_traits_HalfedgeDS.h
+++ b/HalfedgeDS/include/CGAL/boost/graph/graph_traits_HalfedgeDS.h
@@ -111,6 +111,10 @@ struct HDS_edge {
                       i.halfedge():i.halfedge()->opposite());
   }
 
+  friend std::ostream& operator<<(std::ostream& os, const HDS_edge& e)
+  {
+    return os;
+  }
 private:
   Halfedge_handle halfedge_;
 };
diff --git a/STL_Extension/include/CGAL/In_place_list.h b/STL_Extension/include/CGAL/In_place_list.h
index 135fbe1d3c5..7db7f658fe5 100644
--- a/STL_Extension/include/CGAL/In_place_list.h
+++ b/STL_Extension/include/CGAL/In_place_list.h
@@ -111,6 +111,11 @@ namespace internal {
       --*this;
       return tmp;
     }
+
+    friend std::ostream& operator<<(std::ostream& os, const Self& i)
+    {
+      return os;
+    }
   };
 }
 
@@ -171,6 +176,11 @@ namespace internal {
     {
       return In_place_list_iterator<T,Alloc>(const_cast<T*>(node));
     }
+
+    friend std::ostream& operator<<(std::ostream& os, const Self& i)
+    {
+      return os;
+    }
   };
 
 
@@ -189,6 +199,7 @@ template <class T, class Alloc>
     return reinterpret_cast<std::size_t>(ptr)/ sizeof(T);
   }
 
+
 }