diff --git a/Min_sphere_of_spheres_d/include/CGAL/Min_sphere_of_spheres_d/Min_sphere_of_spheres_d_configure.h b/Min_sphere_of_spheres_d/include/CGAL/Min_sphere_of_spheres_d/Min_sphere_of_spheres_d_configure.h
index e3b7f99eef3..c076c8fceda 100644
--- a/Min_sphere_of_spheres_d/include/CGAL/Min_sphere_of_spheres_d/Min_sphere_of_spheres_d_configure.h
+++ b/Min_sphere_of_spheres_d/include/CGAL/Min_sphere_of_spheres_d/Min_sphere_of_spheres_d_configure.h
@@ -66,6 +66,7 @@
 
 // Define some assertion macros used in the code.
 #ifdef CGAL_MINIBALL_DEBUG
+  #include <CGAL/assertions.h>
   #define CGAL_MINIBALL_ASSERT(expr) CGAL_assertion(expr)
   #define CGAL_MINIBALL_DO_DEBUG(expr) expr
 #else