diff --git a/Constrained_triangulation_3/include/CGAL/IO/write_MEDIT.h b/Constrained_triangulation_3/include/CGAL/IO/write_MEDIT.h
index 70d64ea7f4f..95d2262ecd0 100644
--- a/Constrained_triangulation_3/include/CGAL/IO/write_MEDIT.h
+++ b/Constrained_triangulation_3/include/CGAL/IO/write_MEDIT.h
@@ -9,6 +9,11 @@
 //
 // Author(s)     : Jane Tournois
 
+#ifndef CGAL_CONSTRAINED_DELAUNAY_TRIANGULATION_3_IO_WRITE_MEDIT_H
+#define CGAL_CONSTRAINED_DELAUNAY_TRIANGULATION_3_IO_WRITE_MEDIT_H
+
+#include <CGAL/license/Constrained_triangulation_3.h>
+
 #include "CGAL/unordered_flat_map.h"
 #include <CGAL/Conforming_constrained_Delaunay_triangulation_3.h>
 
@@ -107,3 +112,5 @@ void write_MEDIT(std::ostream& os,
 
 }// end namespace IO
 }// end namespace CGAL
+
+#endif // CGAL_CONSTRAINED_DELAUNAY_TRIANGULATION_3_IO_WRITE_MEDIT_H