diff --git a/Convex_decomposition_3/include/CGAL/Convex_decomposition_3/External_structure_builder.h b/Convex_decomposition_3/include/CGAL/Convex_decomposition_3/External_structure_builder.h
index 823a9b7c4ce..8c4c546590d 100644
--- a/Convex_decomposition_3/include/CGAL/Convex_decomposition_3/External_structure_builder.h
+++ b/Convex_decomposition_3/include/CGAL/Convex_decomposition_3/External_structure_builder.h
@@ -17,6 +17,7 @@
 
 
 #include <CGAL/Nef_3/SNC_decorator.h>
+#include <CGAL/Nef_3/SNC_external_structure.h>
 #include <CGAL/Nef_3/SNC_intersection.h>
 
 #undef CGAL_NEF_DEBUG