diff --git a/Cartesian_kernel/include/CGAL/Cartesian/Plane_3.h b/Cartesian_kernel/include/CGAL/Cartesian/Plane_3.h
index ec4ebfff3fd..e69b7ccd008 100644
--- a/Cartesian_kernel/include/CGAL/Cartesian/Plane_3.h
+++ b/Cartesian_kernel/include/CGAL/Cartesian/Plane_3.h
@@ -28,6 +28,7 @@
 #include <CGAL/array.h>
 #include <CGAL/Handle_for.h>
 #include <CGAL/Cartesian/solve_3.h>
+#include <CGAL/Cartesian/plane_constructions_3.h>
 
 namespace CGAL {
 
diff --git a/Cartesian_kernel/include/CGAL/Cartesian/plane_constructions_3.h b/Cartesian_kernel/include/CGAL/Cartesian/plane_constructions_3.h
index 3ba2034b564..5adcb1bdf88 100644
--- a/Cartesian_kernel/include/CGAL/Cartesian/plane_constructions_3.h
+++ b/Cartesian_kernel/include/CGAL/Cartesian/plane_constructions_3.h
@@ -30,6 +30,9 @@
 
 namespace CGAL {
 
+template <class R_>
+class PlaneC3;
+
 template <class R>
 CGAL_KERNEL_LARGE_INLINE
 PlaneC3<R>