diff --git a/Polyhedron/demo/Polyhedron/Plugins/PCA/Scene_polyhedron_transform_item.cpp b/Polyhedron/demo/Polyhedron/Plugins/PCA/Scene_polyhedron_transform_item.cpp
index 3b5ad7959bc..eed9c151034 100644
--- a/Polyhedron/demo/Polyhedron/Plugins/PCA/Scene_polyhedron_transform_item.cpp
+++ b/Polyhedron/demo/Polyhedron/Plugins/PCA/Scene_polyhedron_transform_item.cpp
@@ -1,6 +1,7 @@
 #include "Scene_polyhedron_transform_item.h"
 #include "Kernel_type.h"
 #include "Polyhedron_type.h"
+#include <CGAL/Three/Viewer_interface.h>
 
 Scene_polyhedron_transform_item::Scene_polyhedron_transform_item(const qglviewer::Vec& pos,const Scene_polyhedron_item* poly_item_,const CGAL::Three::Scene_interface*):
     Scene_item(NbOfVbos,NbOfVaos),
diff --git a/Polyhedron/demo/Polyhedron/Plugins/Surface_mesh_deformation/Scene_edit_polyhedron_item.cpp b/Polyhedron/demo/Polyhedron/Plugins/Surface_mesh_deformation/Scene_edit_polyhedron_item.cpp
index 7f477b63da3..aa327419ffc 100644
--- a/Polyhedron/demo/Polyhedron/Plugins/Surface_mesh_deformation/Scene_edit_polyhedron_item.cpp
+++ b/Polyhedron/demo/Polyhedron/Plugins/Surface_mesh_deformation/Scene_edit_polyhedron_item.cpp
@@ -3,6 +3,7 @@
 #include "opengl_tools.h"
 #include "create_sphere.h"
 #include "Scene_edit_polyhedron_item.h"
+#include <CGAL/Three/Viewer_interface.h>
 #include <boost/foreach.hpp>
 #include <algorithm>
 #include <QTime>
diff --git a/Polyhedron/demo/Polyhedron/Scene_nef_polyhedron_item.cpp b/Polyhedron/demo/Polyhedron/Scene_nef_polyhedron_item.cpp
index c27b4661127..0e8d0f4e5bf 100644
--- a/Polyhedron/demo/Polyhedron/Scene_nef_polyhedron_item.cpp
+++ b/Polyhedron/demo/Polyhedron/Scene_nef_polyhedron_item.cpp
@@ -1,4 +1,5 @@
 #include "Scene_nef_polyhedron_item.h"
+#include <CGAL/Three/Viewer_interface.h>
 #include "Scene_polyhedron_item.h"
 #include "Nef_type.h"
 #include "Polyhedron_type.h"
diff --git a/Polyhedron/demo/Polyhedron/Scene_polyhedron_selection_item.h b/Polyhedron/demo/Polyhedron/Scene_polyhedron_selection_item.h
index 5f820793a6e..93a7db30507 100644
--- a/Polyhedron/demo/Polyhedron/Scene_polyhedron_selection_item.h
+++ b/Polyhedron/demo/Polyhedron/Scene_polyhedron_selection_item.h
@@ -14,6 +14,11 @@
 #include <CGAL/Polygon_mesh_processing/connected_components.h>
 #include "Polyhedron_demo_detect_sharp_edges.h"
 
+// Laurent Rineau, 2016/04/07: that header should not be included here, but
+// only in the .cpp file. But that header file does contain the body of a
+// few member functions.
+#include <CGAL/Three/Viewer_interface.h>
+
 #include <fstream>
 #include <boost/foreach.hpp>
 #include <boost/unordered_set.hpp>