diff --git a/Bounding_volumes/include/CGAL/Rectangular_p_center_traits_2.h b/Bounding_volumes/include/CGAL/Rectangular_p_center_traits_2.h
index 8b2c9e70339..bc93c75bf74 100644
--- a/Bounding_volumes/include/CGAL/Rectangular_p_center_traits_2.h
+++ b/Bounding_volumes/include/CGAL/Rectangular_p_center_traits_2.h
@@ -291,8 +291,7 @@ bounding_box_2(ForwardIterator f, ForwardIterator l, const Traits& t)
 } // bounding_box_2(f, l, t)
 template < class ForwardIterator >
 inline
-//typename std::iterator_traits< ForwardIterator >::value_type::R::Iso_rectangle_2
-decltype(auto)
+auto
 bounding_box_2(ForwardIterator f, ForwardIterator l)
 // PRE: f != l.
 {
diff --git a/STL_Extension/include/CGAL/function_objects.h b/STL_Extension/include/CGAL/function_objects.h
index 11bcf352a00..82709ab1265 100644
--- a/STL_Extension/include/CGAL/function_objects.h
+++ b/STL_Extension/include/CGAL/function_objects.h
@@ -358,7 +358,7 @@ public:
   Unary_compose_1(const Op1& x, const Op2& y) : op1(x), op2(y) {}
 
   template <typename argument_type>
-  decltype(auto)
+  auto
   operator()(const argument_type& x) const
   { return op1(op2(x)); }
 };
@@ -381,7 +381,7 @@ public:
   : op1(x), op2(y), op3(z) {}
 
   template <typename argument_type>
-  decltype(auto)
+  auto
   operator()(const argument_type& x) const
   { return op1(op2(x), op3(x)); }
 };
@@ -402,7 +402,7 @@ public:
   Unary_compose_2(const Op1& x, const Op2& y) : op1(x), op2(y) {}
 
   template <typename first_argument_type, typename second_argument_type>
-  decltype(auto)
+  auto
   operator()(const first_argument_type& x,
              const second_argument_type& y) const
   { return op1(op2(x, y)); }
@@ -440,7 +440,7 @@ public:
   }
 
   template <typename first_argument_type, typename second_argument_type>
-  decltype(auto)
+  auto
   operator()(const first_argument_type& x,
              const second_argument_type& y) const
   { return op1(op2(x), op3(y)); }