diff --git a/Kernel_23/include/CGAL/Circle_2.h b/Kernel_23/include/CGAL/Circle_2.h
index e28e209932a..118412419e8 100644
--- a/Kernel_23/include/CGAL/Circle_2.h
+++ b/Kernel_23/include/CGAL/Circle_2.h
@@ -28,6 +28,7 @@
 #include <boost/static_assert.hpp>
 #include <boost/type_traits.hpp>
 #include <CGAL/Kernel/Return_base_tag.h>
+#include <CGAL/Bbox_2.h>
 
 CGAL_BEGIN_NAMESPACE
 
diff --git a/Kernel_23/include/CGAL/Iso_rectangle_2.h b/Kernel_23/include/CGAL/Iso_rectangle_2.h
index dcfeae7d326..c7767b04532 100644
--- a/Kernel_23/include/CGAL/Iso_rectangle_2.h
+++ b/Kernel_23/include/CGAL/Iso_rectangle_2.h
@@ -27,6 +27,7 @@
 #include <boost/static_assert.hpp>
 #include <boost/type_traits.hpp>
 #include <CGAL/Kernel/Return_base_tag.h>
+#include <CGAL/Bbox_2.h>
 
 CGAL_BEGIN_NAMESPACE