diff --git a/Mesh_2/include/CGAL/Mesh_2/Mesh_global_optimizer_2.h b/Mesh_2/include/CGAL/Mesh_2/Mesh_global_optimizer_2.h
index a16d221a6b8..4c6dacd7802 100644
--- a/Mesh_2/include/CGAL/Mesh_2/Mesh_global_optimizer_2.h
+++ b/Mesh_2/include/CGAL/Mesh_2/Mesh_global_optimizer_2.h
@@ -108,7 +108,7 @@ public:
     }
   }
 
-  Mesh_optimization_return_code operator()(const int nb_iterations)
+  Mesh_optimization_return_code operator()(const std::size_t nb_iterations)
   {
     running_time_.reset();
     running_time_.start();
@@ -141,7 +141,7 @@ public:
     bool convergence_stop = false;
 
     // Iterate
-    int i = -1;
+    std::size_t i = -1;
     while ( ++i < nb_iterations && ! is_time_limit_reached() )
     {
       this->before_move();
diff --git a/Mesh_2/include/CGAL/lloyd_optimize_mesh_2.h b/Mesh_2/include/CGAL/lloyd_optimize_mesh_2.h
index e145b6524e8..fe7a7c321ac 100644
--- a/Mesh_2/include/CGAL/lloyd_optimize_mesh_2.h
+++ b/Mesh_2/include/CGAL/lloyd_optimize_mesh_2.h
@@ -190,7 +190,7 @@ lloyd_optimize_mesh_2(CDT& cdt, const CGAL_NP_CLASS& np = parameters::default_va
   template<typename CDT>
   Mesh_optimization_return_code
   lloyd_optimize_mesh_2_impl(CDT& cdt,
-                             const int max_iterations,
+                             const std::size_t max_iterations,
                              const double convergence_ratio,
                              const double freeze_bound,
                              const double time_limit,
@@ -206,7 +206,7 @@ lloyd_optimize_mesh_2(CDT& cdt, const CGAL_NP_CLASS& np = parameters::default_va
   template<typename CDT, typename InputIterator>
   Mesh_optimization_return_code
   lloyd_optimize_mesh_2_impl(CDT& cdt,
-                             const int max_iterations,
+                             const std::size_t max_iterations,
                              const double convergence_ratio,
                              const double freeze_bound,
                              const double time_limit,
@@ -231,7 +231,7 @@ lloyd_optimize_mesh_2(CDT& cdt, const CGAL_NP_CLASS& np = parameters::default_va
 #endif
 
     // 1000 iteration max to avoid infinite loop
-    int nb_iterations = (0 == max_iterations)
+    std::size_t nb_iterations = (0 == max_iterations)
       ? 1000
       : max_iterations;
 
diff --git a/Mesh_2/test/Mesh_2/test_double_map.cpp b/Mesh_2/test/Mesh_2/test_double_map.cpp
index 7ef6a121834..f7f82d21647 100644
--- a/Mesh_2/test/Mesh_2/test_double_map.cpp
+++ b/Mesh_2/test/Mesh_2/test_double_map.cpp
@@ -12,7 +12,7 @@ typedef CGAL::Double_map<int, int> Map;
 
 int main(int argc, char** argv)
 {
-  unsigned int number_of_elements = 500;
+  int number_of_elements = 500;
 
 #ifdef CGAL_USE_BOOST_BIMAP
   std::cerr << "(Using the \"Boost.Bimap implementation\" of <CGAL/Double_map.h>...)\n\n";
@@ -58,14 +58,14 @@ int main(int argc, char** argv)
   assert(f.empty() && f2.empty());
   /* AUTOMATIC CHECKS */
   std::cerr << "Filling f with " << number_of_elements << " random integers...\n";
-  for(unsigned int n=0; n<number_of_elements; n++)
+  for(int n=0; n<number_of_elements; n++)
   {
     int i=CGAL::get_default_random().get_int(0,1000);
     f.insert(i, i*i);
   }
 
   std::cerr << "Check f.size<=" << number_of_elements << ".\n";
-  assert(f.size()<=number_of_elements);
+  assert(f.size()<=std::size_t(number_of_elements));
 
   std::cerr << "Assignment f2=f...\n";
   f2 = f; // check the assignment
@@ -123,18 +123,18 @@ int main(int argc, char** argv)
   assert(f3.empty());
 
   std::cerr << "Filling f with f(i)=i*i, i=0.." << number_of_elements-1 << "...\n";
-  for(unsigned int n=0; n<number_of_elements; n++)
+  for(int n=0; n<number_of_elements; n++)
   {
     f.insert(n, n*n);
   }
 
   std::cerr << "Check size: "
             << "f.size()=" << f.size() << "\n";
-  assert(f.size()==number_of_elements);
+  assert(f.size()==std::size_t(number_of_elements));
 
   std::cerr << "Emptying f...\n";
   i2=0;
-  unsigned int counter = 0;
+  int counter = 0;
   while(!f.empty())
   {
     int i = f.front()->second;
@@ -152,7 +152,7 @@ int main(int argc, char** argv)
   assert(counter==number_of_elements);
 
   std::cerr << "Filling f with f(i)=i*i, i=0.." << number_of_elements -1 << "...\n";
-  for(unsigned int n=0; n<number_of_elements; n++)
+  for(int n=0; n<number_of_elements; n++)
   {
     f.insert(n, n*n);
   }