diff --git a/Mesh_3/include/CGAL/Mesh_3/polylines_to_protect.h b/Mesh_3/include/CGAL/Mesh_3/polylines_to_protect.h
index d959375ae3e..dbffdb4c547 100644
--- a/Mesh_3/include/CGAL/Mesh_3/polylines_to_protect.h
+++ b/Mesh_3/include/CGAL/Mesh_3/polylines_to_protect.h
@@ -28,6 +28,8 @@
 #include <boost/graph/adjacency_list.hpp>
 
 #include <CGAL/number_utils.h>
+#include <CGAL/squared_distance_3.h>
+
 #include <boost/utility.hpp> // for boost::prior
 #include <boost/optional.hpp>