diff --git a/libisofs/ecma119.c b/libisofs/ecma119.c
index 739f8d5..1176e81 100644
--- a/libisofs/ecma119.c
+++ b/libisofs/ecma119.c
@@ -1946,6 +1946,7 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *in_opts, Ecma119Image **img)
         target->gpt_req[i] = NULL;
     target->gpt_req_count = 0;
     target->gpt_req_flags = 0;
+    target->gpt_disk_guid_set = 0;
     target->gpt_part_start = 0;
     target->gpt_backup_end = 0;
     target->gpt_backup_size = 0;
diff --git a/libisofs/ecma119.h b/libisofs/ecma119.h
index 8006536..a9968e8 100644
--- a/libisofs/ecma119.h
+++ b/libisofs/ecma119.h
@@ -808,6 +808,8 @@ struct ecma119_image
     /* Messages from gpt_tail_writer_compute_data_blocks() to
        iso_write_system_area().
     */
+    uint8_t gpt_disk_guid[16];
+    int gpt_disk_guid_set;
     /* Start of GPT entries in System Area, block size 512 */
     uint32_t gpt_part_start;
     /* The ISO block number after the backup GPT header , block size 2048 */
diff --git a/libisofs/system_area.c b/libisofs/system_area.c
index cc5555c..61e7919 100644
--- a/libisofs/system_area.c
+++ b/libisofs/system_area.c
@@ -1385,11 +1385,9 @@ static void iso_write_gpt_entry(Ecma119Image *t, uint8_t *buf,
     for (i = 0; i < 16; i++)
         if (part_uuid[i])
     break;
-    if (i < 16) {
-        memcpy(wpt, part_uuid, 16);
-    } else {
-        iso_random_uuid(t, (uint8_t *) wpt);
-    }
+    if (i == 16)
+        iso_random_uuid(t, part_uuid);
+    memcpy(wpt, part_uuid, 16);
     wpt += 16;
     iso_lsb_to_buf(&wpt, start_lba & 0xffffffff, 4, 0);
     iso_lsb_to_buf(&wpt, (start_lba >> 32) & 0xffffffff, 4, 0);
@@ -1450,7 +1448,10 @@ int iso_write_gpt_header_block(Ecma119Image *t, uint32_t img_blocks,
 
     /* Disk GUID */
     /* >>> Make adjustable */
-    iso_random_uuid(t, (uint8_t *) wpt);
+    if (!t->gpt_disk_guid_set)
+        iso_random_uuid(t, t->gpt_disk_guid);
+    t->gpt_disk_guid_set = 1;
+    memcpy(wpt, t->gpt_disk_guid, 16);
     wpt += 16;
 
     /* Partition entries start */