diff --git a/harbour/ChangeLog b/harbour/ChangeLog
index 58dab977db..7f7b533707 100644
--- a/harbour/ChangeLog
+++ b/harbour/ChangeLog
@@ -16,6 +16,16 @@
    The license applies to all entries newer than 2009-04-28.
 */
 
+2010-06-18 10:58 UTC+0200 Viktor Szakats (harbour.01 syenar.hu)
+  * include/hbdefs.h
+    + HB_SIZE/HB_ISIZ set to 64-bit value on Win64 targets.
+      This change should finally fix the many casting errors appearing
+      in Win64 builds of Harbour, plus it enables to use proper 64-bit
+      sizes for strings and arrays.
+    ; TODO: Test and fix and places where this may cause a problem.
+            Delete all now unnecessary casting from size_t to HB_SIZE.
+            (f.e. '( HB_SIZE ) strlen(')
+
 2010-06-18 10:50 UTC+0200 Viktor Szakats (harbour.01 syenar.hu)
   * include/hbdefs.h
     + Rearranged types to first define base Harbour types, then
diff --git a/harbour/include/hbdefs.h b/harbour/include/hbdefs.h
index 9dccf8f84b..26945c5032 100644
--- a/harbour/include/hbdefs.h
+++ b/harbour/include/hbdefs.h
@@ -232,6 +232,7 @@
 
 #endif /* HB_LONG_LONG_OFF */
 
+/* Basic types */
 #define HB_FALSE 0
 #define HB_TRUE  (!0)
 
@@ -244,8 +245,15 @@ typedef long                HB_LONG;           /* WARNING: These types have a ne
 typedef unsigned long       HB_ULONG;          /* WARNING: These types have a new size in Harbour 2.1.x and upper. */
 typedef int                 HB_INT;
 typedef unsigned int        HB_UINT;
-typedef unsigned long       HB_SIZE;           /* TODO: Currently 'unsigned long', to be changed to HB_LONGLONG on win64, long on other systems */
-typedef long                HB_ISIZ;           /* TODO: Change to HB_SIZE, after HB_SIZE has been converted to signed type. TEMPORARY type. */
+
+/* Harbour size type */
+#if defined( HB_OS_WIN_64 )
+   typedef HB_ULONGLONG        HB_SIZE;           /* TODO: Currently 'unsigned', to be changed 'signed' */
+   typedef HB_LONGLONG         HB_ISIZ;           /* TODO: Change to HB_SIZE, after HB_SIZE has been converted to signed type. TEMPORARY type. */
+#else
+   typedef HB_ULONG            HB_SIZE;           /* TODO: Currently 'unsigned', to be changed 'signed' */
+   typedef HB_LONG             HB_ISIZ;           /* TODO: Change to HB_SIZE, after HB_SIZE has been converted to signed type. TEMPORARY type. */
+#endif
 
 /* Convenience */
 typedef HB_UCHAR            HB_BYTE;