diff --git a/Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/marching_cubes_functors.h b/Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/marching_cubes_functors.h
index 1767c01da2c..1c6dd8e53c1 100644
--- a/Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/marching_cubes_functors.h
+++ b/Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/marching_cubes_functors.h
@@ -179,14 +179,14 @@ void MC_construct_vertices(const typename Domain::cell_descriptor& cell,
 // connects the vertices of one cell to form triangles
 template <typename Vertices,
           typename TriangleList>
-void MC_construct_triangles(const int i_case,
+void MC_construct_triangles(const std::size_t i_case,
                             const Vertices& vertices,
                             TriangleList& triangles)
 {
   // construct triangles
   for(int t=0; t<16; t+=3)
   {
-    const int t_index = i_case * 16 + t;
+    const std::size_t t_index = i_case * 16 + t;
 
     // if(e_tris_list[t_index] == 0x7f)
     if(Cube_table::triangle_cases[t_index] == -1)
diff --git a/Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/topologically_correct_marching_cubes_functors.h b/Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/topologically_correct_marching_cubes_functors.h
index 0a33b5b8c49..a80e25dc6aa 100644
--- a/Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/topologically_correct_marching_cubes_functors.h
+++ b/Isosurfacing_3/include/CGAL/Isosurfacing_3/internal/topologically_correct_marching_cubes_functors.h
@@ -172,7 +172,7 @@ public:
     // construct triangles
     for(int t=0; t<16; t+=3)
     {
-      const int t_index = i_case * 16 + t;
+      const std::size_t t_index = i_case * 16 + t;
 
       // if(e_tris_list[t_index] == 0x7f)
       if(Cube_table::triangle_cases[t_index] == -1)
@@ -297,7 +297,7 @@ private:
                const FT i0,
                const std::array<Point_3, 8>& corners,
                const std::array<FT, 8>& values,
-               const int i_case)
+               const std::size_t i_case)
   {
     typename Geom_traits::Compute_x_3 x_coord = m_domain.geom_traits().compute_x_3_object();
     typename Geom_traits::Compute_y_3 y_coord = m_domain.geom_traits().compute_y_3_object();