diff --git a/doc/boot_sectors.txt b/doc/boot_sectors.txt
index 8e336c2..d22f376 100644
--- a/doc/boot_sectors.txt
+++ b/doc/boot_sectors.txt
@@ -895,7 +895,7 @@ Sources:
     Mail conversations with Vladimir Serbinenko.
 
 
-PReP boots via a MBR partition containing only raw ELF and having type 0x41.
+PReP boots via a MBR partition containing only raw ELF and having type 0x42.
 
 
 ------------------------------------------------------------------------------
@@ -1376,7 +1376,7 @@ System Area may contain simultaneously:
 
 MBR Partitions:
    0xee from    0 to PREP-1, protective partition, announcing presence of GPT
-   0x41 from PREP to HFAT-1, PreP partition
+   0x42 from PREP to HFAT-1, PreP partition
    0x0c from HFAT to  END-1, FAT partition, bootable bit on
    0x00                      Empty partition
 
diff --git a/libisofs/system_area.c b/libisofs/system_area.c
index c7804e2..50addc6 100644
--- a/libisofs/system_area.c
+++ b/libisofs/system_area.c
@@ -2091,7 +2091,7 @@ static int partprepend_writer_compute_data_blocks(IsoImageWriter *writer)
             return ret;
     }
     if (t->prep_part_size > 0) {
-        ret = iso_quick_mbr_entry(t, t->curblock, t->prep_part_size, 0x41, 0);
+        ret = iso_quick_mbr_entry(t, t->curblock, t->prep_part_size, 0x42, 0);
         if (ret < 0)
             return ret;
         t->curblock += t->prep_part_size;