diff --git a/Packages/Kernel_d/changes.txt b/Packages/Kernel_d/changes.txt
index 75513739d5c..c6f69de7cc5 100644
--- a/Packages/Kernel_d/changes.txt
+++ b/Packages/Kernel_d/changes.txt
@@ -1,5 +1,8 @@
 Kernel_d Package: Release changes
 ----------------------------------------------------------------------
+0.9.64 (17 April 2002)
+   added missing std:: before ptrdiff_t  in Regular_complex....h
+
 0.9.63 (17 April 2002)
    removed SIMPLE_INTERFACE for Borland in Vector__.h
 
diff --git a/Packages/Kernel_d/include/CGAL/Regular_complex_d.h b/Packages/Kernel_d/include/CGAL/Regular_complex_d.h
index 7530ef95c7f..54926455bc9 100644
--- a/Packages/Kernel_d/include/CGAL/Regular_complex_d.h
+++ b/Packages/Kernel_d/include/CGAL/Regular_complex_d.h
@@ -42,6 +42,7 @@
 #include <CGAL/In_place_list.h>
 #include <vector>
 #include <list>
+#include <cstddef>
 
 #undef _DEBUG
 #define _DEBUG 93