diff --git a/Polyhedron/demo/Polyhedron/Plugins/Point_set/Surface_reconstruction_plugin.cpp b/Polyhedron/demo/Polyhedron/Plugins/Point_set/Surface_reconstruction_plugin.cpp
index 63003bb8cdb..6b0d61b56ec 100644
--- a/Polyhedron/demo/Polyhedron/Plugins/Point_set/Surface_reconstruction_plugin.cpp
+++ b/Polyhedron/demo/Polyhedron/Plugins/Point_set/Surface_reconstruction_plugin.cpp
@@ -22,7 +22,6 @@
 #include <CGAL/Search_traits_3.h>
 #include <CGAL/squared_distance_3.h>
 #include <CGAL/Orthogonal_k_neighbor_search.h>
-#include <CGAL/Default_diagonalize_traits.h>
 #include <CGAL/compute_average_spacing.h>
 #include <CGAL/grid_simplify_point_set.h>
 #include <CGAL/jet_smooth_point_set.h>
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_circles_2.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_circles_2.cpp
index b2f2c69575f..baa560c2f3f 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_circles_2.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_circles_2.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // Example program for the linear_least_square_fitting function on a set of circles in 2D
 
 #include <CGAL/Cartesian.h>
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_cuboids_3.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_cuboids_3.cpp
index caad6d8dbc9..eb3c32e8a9f 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_cuboids_3.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_cuboids_3.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // Example program for the linear_least_square_fitting function on set of cuboids in 3D
 #include <CGAL/Cartesian.h>
 #include <CGAL/linear_least_squares_fitting_3.h>
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_points_2.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_points_2.cpp
index b8aa1207cc3..d5a243c9e62 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_points_2.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_points_2.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // test for the linear_least_square_fitting() functions.
 #include <CGAL/Cartesian.h>
 #include <CGAL/algorithm.h>
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_points_3.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_points_3.cpp
index bd94792cf91..55dbb420c6b 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_points_3.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_points_3.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // test for the linear_least_square_fitting() functions.
 
 
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_rectangles_2.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_rectangles_2.cpp
index 5b7d67f01ce..c735e6b658c 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_rectangles_2.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_rectangles_2.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // test for the linear_least_square_fitting() functions.
 
 
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_segments_2.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_segments_2.cpp
index 9a4d6fe8a90..292018f05eb 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_segments_2.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_segments_2.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // test for the linear_least_square_fitting() functions.
 
 
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_segments_3.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_segments_3.cpp
index 260eae89b21..f3e58e21d7e 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_segments_3.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_segments_3.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // test for the linear_least_square_fitting() functions.
 
 
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_spheres_3.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_spheres_3.cpp
index 044de1a2c91..9037ba236a9 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_spheres_3.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_spheres_3.cpp
@@ -1,5 +1,7 @@
 // Example program for the linear_least_square_fitting function
 
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 #include <CGAL/Cartesian.h>
 #include <CGAL/linear_least_squares_fitting_3.h>
 #ifdef CGAL_EIGEN3_ENABLED
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_tetrahedra_3.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_tetrahedra_3.cpp
index 560be170c05..a2150baf22d 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_tetrahedra_3.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_tetrahedra_3.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // Example program for the linear_least_square_fitting function
 // on a set of tetrahedra in 3D
 
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_triangles_2.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_triangles_2.cpp
index 37d3b15a89a..e45305b1a99 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_triangles_2.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_triangles_2.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // test for the linear_least_square_fitting() functions.
 #include <CGAL/Cartesian.h>
 #include <CGAL/algorithm.h>
diff --git a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_triangles_3.cpp b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_triangles_3.cpp
index a075a75699f..d210dce1f08 100644
--- a/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_triangles_3.cpp
+++ b/Principal_component_analysis/test/Principal_component_analysis/test_linear_least_squares_fitting_triangles_3.cpp
@@ -1,3 +1,5 @@
+#define CGAL_NO_DEPRECATION_WARNINGS
+
 // Example program for the linear_least_square_fitting function on set of triangles in 3D
 #include <CGAL/Cartesian.h>
 #include <CGAL/linear_least_squares_fitting_3.h>
diff --git a/Solver_interface/doc/Solver_interface/PackageDescription.txt b/Solver_interface/doc/Solver_interface/PackageDescription.txt
index 663a5c99f33..c8cb3e86a2d 100644
--- a/Solver_interface/doc/Solver_interface/PackageDescription.txt
+++ b/Solver_interface/doc/Solver_interface/PackageDescription.txt
@@ -31,10 +31,8 @@
 
 ## Classes ##
 
-- `CGAL::Diagonalize_traits`
 - `CGAL::Eigen_solver_traits`
 - `CGAL::Eigen_diagonalize_traits`
-- `CGAL::Default_diagonalize_traits`
 - `CGAL::Eigen_vector`
 - `CGAL::Eigen_matrix`
 - `CGAL::Eigen_sparse_matrix`
diff --git a/Solver_interface/examples/Solver_interface/diagonalize_matrix.cpp b/Solver_interface/examples/Solver_interface/diagonalize_matrix.cpp
index 21d6a4925f4..1fbada87dc0 100644
--- a/Solver_interface/examples/Solver_interface/diagonalize_matrix.cpp
+++ b/Solver_interface/examples/Solver_interface/diagonalize_matrix.cpp
@@ -1,22 +1,13 @@
 #include <iostream>
 
-#ifdef CGAL_EIGEN3_ENABLED
 #include <CGAL/Eigen_diagonalize_traits.h>
-#else
-#include <CGAL/Diagonalize_traits.h>
-#endif
 
 typedef double                                          FT;
 typedef CGAL::cpp11::array<FT, 6>                       Eigen_matrix;
 typedef CGAL::cpp11::array<FT, 3>                       Eigen_vector;
 typedef CGAL::cpp11::array<FT, 9>                       Eigen_three_vectors;
 
-// If Eigen is enabled, use it, otherwise fallback to the internal model
-#ifdef CGAL_EIGEN3_ENABLED
 typedef CGAL::Eigen_diagonalize_traits<FT, 3>           Diagonalize_traits;
-#else
-typedef CGAL::Diagonalize_traits<FT, 3>                 Diagonalize_traits;
-#endif
 
 int main(void)
 {