diff --git a/libisofs/ecma119.c b/libisofs/ecma119.c
index b275ba7..4ab02ec 100644
--- a/libisofs/ecma119.c
+++ b/libisofs/ecma119.c
@@ -1374,6 +1374,8 @@ ex:
 
 /* @param flag bit0= initialize system area by target->opts_overwrite
                bit1= fifo is not yet draining. Inquire write_count from fifo.
+               bit2= target->opts->ms_block is not counted in
+                     target->total_size
 */
 static
 int write_head_part1(Ecma119Image *target, int *write_count, int flag)
@@ -1396,7 +1398,7 @@ int write_head_part1(Ecma119Image *target, int *write_count, int flag)
     /* Write System Area (ECMA-119, 6.2.1) */
     if ((flag & 1) && target->opts_overwrite != NULL)
         memcpy(sa, target->opts_overwrite, 16 * BLOCK_SIZE);
-    res = iso_write_system_area(target, sa);
+    res = iso_write_system_area(target, sa, (flag & 4) >> 2);
     if (res < 0)
         goto write_error;
     res = iso_write(target, sa, 16 * BLOCK_SIZE);
@@ -1500,7 +1502,7 @@ int write_head_part(Ecma119Image *target, int flag)
     int res, write_count = 0;
 
     /* System area and volume descriptors */
-    res = write_head_part1(target, &write_count, 0);
+    res = write_head_part1(target, &write_count, 4);
     if (res < 0)
         return res;
 
diff --git a/libisofs/system_area.c b/libisofs/system_area.c
index c843430..55890cc 100644
--- a/libisofs/system_area.c
+++ b/libisofs/system_area.c
@@ -1875,7 +1875,10 @@ static void iso_dummy_mbr_partition(uint8_t *buf, int mode)
 }
 
 
-int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
+/* @param flag
+          bit0= t->opts->ms_block is not counted in t->total_size
+*/
+int iso_write_system_area(Ecma119Image *t, uint8_t *buf, int flag)
 {
     int ret, int_img_blocks, sa_type, i, will_append = 0, do_isohybrid = 0;
     int first_partition = 1, last_partition = 4, apm_flag, part_type = 0;
@@ -1984,7 +1987,8 @@ int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
     }
 
     if (t->gpt_backup_outside)
-        gpt_blocks = t->total_size / BLOCK_SIZE + t->opts->ms_block;
+        gpt_blocks = t->total_size / BLOCK_SIZE +
+                     (flag & 1) * t->opts->ms_block;
     else
         gpt_blocks = img_blocks;
     ret = iso_write_gpt(t, gpt_blocks, buf);
@@ -2146,7 +2150,8 @@ int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
 #endif
 
         if (part_type == 0xee && t->gpt_req_count > 0) {
-            mbrp1_blocks = t->total_size / BLOCK_SIZE + t->opts->ms_block;
+            mbrp1_blocks = t->total_size / BLOCK_SIZE +
+                           (flag & 1) * t->opts->ms_block;
             offset_flag |= 2 | 1; /* protective MBR, no other partitions */
         } else {
             mbrp1_blocks = img_blocks;
diff --git a/libisofs/system_area.h b/libisofs/system_area.h
index 382b396..a91edbb 100644
--- a/libisofs/system_area.h
+++ b/libisofs/system_area.h
@@ -42,10 +42,12 @@ int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag);
  *
  * @param buf
  *      A buffer with at least 32 K allocated
+ * @param flag
+ *      bit0= t->opts->ms_block is not counted in t->total_size
  * @return
  *      1 if success, < 0 on error
  */
-int iso_write_system_area(Ecma119Image *t, uint8_t *buf);
+int iso_write_system_area(Ecma119Image *t, uint8_t *buf, int flag);
 
 /**
  * Adjust t->tail_blocks to the eventual alignment needs of isohybrid booting.