diff --git a/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_2.cpp b/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_2.cpp
index 2d133ddba86..81562b974fd 100644
--- a/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_2.cpp
+++ b/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_2.cpp
@@ -5,6 +5,7 @@
 #include <CGAL/Exact_rational.h>
 #include <CGAL/Min_sphere_of_spheres_d.h>
 #include <vector>
+#include <cassert>
 
 const int N = 1000;                       // number of spheres
 const int LOW = 0, HIGH = 10000;          // range of coordinates and radii
@@ -29,5 +30,5 @@ int main () {
   }
 
   Min_sphere ms(S.begin(),S.end());       // check in the spheres
-  CGAL_assertion(ms.is_valid());
+  assert(ms.is_valid());
 }
diff --git a/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_3.cpp b/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_3.cpp
index c0b8b978e0c..a8a998a991f 100644
--- a/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_3.cpp
+++ b/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_3.cpp
@@ -5,6 +5,7 @@
 #include <CGAL/Exact_rational.h>
 #include <CGAL/Min_sphere_of_spheres_d.h>
 #include <vector>
+#include <cassert>
 
 const int N = 1000;                       // number of spheres
 const int LOW = 0, HIGH = 10000;          // range of coordinates and radii
@@ -30,5 +31,5 @@ int main () {
   }
 
   Min_sphere ms(S.begin(),S.end());       // check in the spheres
-  CGAL_assertion(ms.is_valid());
+  assert(ms.is_valid());
 }
diff --git a/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_d.cpp b/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_d.cpp
index 0ddbe825fba..984ce89e8e5 100644
--- a/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_d.cpp
+++ b/Bounding_volumes/examples/Min_sphere_of_spheres_d/min_sphere_of_spheres_d_d.cpp
@@ -5,6 +5,7 @@
 #include <CGAL/Exact_rational.h>
 #include <CGAL/Min_sphere_of_spheres_d.h>
 #include <vector>
+#include <cassert>
 
 const int N = 1000;                       // number of spheres
 const int D = 3;                          // dimension of points
@@ -31,5 +32,5 @@ int main () {
   }
 
   Min_sphere ms(S.begin(),S.end());       // check in the spheres
-  CGAL_assertion(ms.is_valid());
+  assert(ms.is_valid());
 }