diff --git a/Straight_skeleton_2/include/CGAL/Arrange_offset_polygons_2.h b/Straight_skeleton_2/include/CGAL/Arrange_offset_polygons_2.h
index 5274281a0c8..6757afb6d4a 100644
--- a/Straight_skeleton_2/include/CGAL/Arrange_offset_polygons_2.h
+++ b/Straight_skeleton_2/include/CGAL/Arrange_offset_polygons_2.h
@@ -19,6 +19,7 @@
 #ifndef CGAL_ARRANGE_OFFSET_POLYGONS_2_H
 #define CGAL_ARRANGE_OFFSET_POLYGONS_2_H
 
+#include <boost/shared_ptr.hpp>
 #include <CGAL/Polygon_with_holes_2.h>
 
 CGAL_BEGIN_NAMESPACE