diff --git a/Filtered_kernel/include/CGAL/Filtered_kernel/Cartesian_coordinate_iterator_2.h b/Filtered_kernel/include/CGAL/Filtered_kernel/Cartesian_coordinate_iterator_2.h
index eab2ae4c986..fbcf154187b 100644
--- a/Filtered_kernel/include/CGAL/Filtered_kernel/Cartesian_coordinate_iterator_2.h
+++ b/Filtered_kernel/include/CGAL/Filtered_kernel/Cartesian_coordinate_iterator_2.h
@@ -49,7 +49,7 @@ public:
 
   typedef std::random_access_iterator_tag iterator_category;
   typedef FT                              value_type;
-  typedef std::ptrdiff_t                  difference_type;
+  typedef int                             difference_type;
   typedef const value_type&               reference;
   typedef const value_type*               pointer;
 
@@ -68,7 +68,7 @@ public:
     if (const P* const* p = boost::get<const P*>(&var))
       return (*p)->cartesian(index);
     const V* const* v = boost::get<const V*>(&var);
-    CGAL_assertion(v);
+    CGAL_assertion(v != 0);
     return (*v)->cartesian(index);
   }
 
diff --git a/Filtered_kernel/include/CGAL/Filtered_kernel/Cartesian_coordinate_iterator_3.h b/Filtered_kernel/include/CGAL/Filtered_kernel/Cartesian_coordinate_iterator_3.h
index 604e7f57bf9..3598162edfe 100644
--- a/Filtered_kernel/include/CGAL/Filtered_kernel/Cartesian_coordinate_iterator_3.h
+++ b/Filtered_kernel/include/CGAL/Filtered_kernel/Cartesian_coordinate_iterator_3.h
@@ -47,7 +47,7 @@ public:
 
   typedef std::random_access_iterator_tag iterator_category;
   typedef FT                              value_type;
-  typedef std::ptrdiff_t                  difference_type;
+  typedef int                             difference_type;
   typedef const value_type&               reference;
   typedef const value_type*               pointer;