diff --git a/Kernel_23/include/CGAL/Vector_3.h b/Kernel_23/include/CGAL/Vector_3.h
index 168ebd12212..7c938415f99 100644
--- a/Kernel_23/include/CGAL/Vector_3.h
+++ b/Kernel_23/include/CGAL/Vector_3.h
@@ -25,6 +25,7 @@
 #define CGAL_VECTOR_3_H
 
 #include <CGAL/Origin.h>
+#include <CGAL/Kernel/mpl.h>
 
 CGAL_BEGIN_NAMESPACE