diff --git a/ChangeLog b/ChangeLog
index 24dbdbf31..38b9ffed1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2009-11-02  Samuel Thibault  <samuel.thibault@ens-lyon.org>
+
+	* util/hostdisk.c (grub_util_biosdisk_get_grub_dev): Subtract 1 from
+	GNU partition number to get internal GRUB partition number.
+
 2009-11-02  Samuel Thibault  <samuel.thibault@ens-lyon.org>
 
 	* util/grub.d/10_hurd.in: Call prepare_grub_to_access_device
diff --git a/util/hostdisk.c b/util/hostdisk.c
index 22b856e29..e1058a100 100644
--- a/util/hostdisk.c
+++ b/util/hostdisk.c
@@ -1057,7 +1057,7 @@ grub_util_biosdisk_get_grub_dev (const char *os_dev)
 	n = strtol (p, &q, 10);
 	if (p != q && n != GRUB_LONG_MIN && n != GRUB_LONG_MAX)
 	  {
-	    dos_part = (int) n;
+	    dos_part = (int) n - 1;
 
 	    if (*q >= 'a' && *q <= 'g')
 	      bsd_part = *q - 'a';