Index: grub-2.00/grub-core/loader/i386/pc/chainloader.c
===================================================================
--- grub-2.00.orig/grub-core/loader/i386/pc/chainloader.c
+++ grub-2.00/grub-core/loader/i386/pc/chainloader.c
@@ -39,6 +39,7 @@
 #include <grub/fat.h>
 #include <grub/ntfs.h>
 #include <grub/i386/relocator.h>
+#include <grub/env.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -149,6 +150,7 @@ grub_chainloader_cmd (const char *filena
   int drive = -1;
   grub_addr_t part_addr = 0;
   grub_uint8_t *bs, *ptable;
+  const char *biosnum;
 
   rel = grub_relocator_new ();
   if (!rel)
@@ -198,11 +200,28 @@ grub_chainloader_cmd (const char *filena
       goto fail;
     }
 
-  grub_file_close (file);
 
-  /* Obtain the partition table from the root device.  */
-  drive = grub_get_root_biosnumber ();
-  dev = grub_device_open (0);
+  /* Obtain the partition table from the loaded device.  */
+  dev = file->device;
+  biosnum = grub_env_get ("biosnum");
+
+  if (biosnum)
+    {
+      drive = grub_strtoul (biosnum, 0, 0);
+    }
+  else
+    {
+      if (dev->disk && dev->disk->dev
+          && dev->disk->dev->id == GRUB_DISK_DEVICE_BIOSDISK_ID)
+        drive = (int) dev->disk->id;
+    }
+
+  if (drive == -1)
+    {
+      grub_error (GRUB_ERR_BAD_NUMBER, "invalid biosnum");
+      goto fail;
+    }
+
   if (dev && dev->disk && dev->disk->partition)
     {
       grub_disk_t disk = dev->disk;
@@ -225,15 +244,14 @@ grub_chainloader_cmd (const char *filena
   if (flags & GRUB_CHAINLOADER_BPB)
     grub_chainloader_patch_bpb ((void *) 0x7C00, dev, drive);
 
-  if (dev)
-    grub_device_close (dev);
- 
   /* Ignore errors. Perhaps it's not fatal.  */
   grub_errno = GRUB_ERR_NONE;
 
   boot_drive = drive;
   boot_part_addr = part_addr;
 
+  grub_file_close (file);
+
   grub_loader_set (grub_chainloader_boot, grub_chainloader_unload, 1);
   return;