diff --git a/ChangeLog b/ChangeLog
index accdd4c67..4780ec1ea 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2013-08-22  Vladimir Serbinenko  <phcoder@gmail.com>
+
+	* include/grub/zfs/spa.h (zio_cksum): Add explicit members for mac.
+	* grub-core/fs/zfs/zfs.c (zio_read): Don't use casts to retrieve mac.
+
 2013-08-22  Vladimir Serbinenko  <phcoder@gmail.com>
 
 	* grub-core/kern/emu/mm.c (grub_memalign): Don't define if there is no
diff --git a/grub-core/fs/zfs/zfs.c b/grub-core/fs/zfs/zfs.c
index f4acfd827..7302b0af5 100644
--- a/grub-core/fs/zfs/zfs.c
+++ b/grub-core/fs/zfs/zfs.c
@@ -1871,7 +1871,7 @@ zio_read (blkptr_t *bp, grub_zfs_endian_t endian, void **buf,
 	  err = grub_zfs_decrypt (data->subvol.keyring[besti].cipher,
 				  data->subvol.keyring[besti].algo,
 				  &(bp)->blk_dva[encrypted],
-				  compbuf, psize, ((grub_uint32_t *) &zc + 5),
+				  compbuf, psize, zc.zc_mac,
 				  endian);
 	}
       if (err)
diff --git a/include/grub/zfs/spa.h b/include/grub/zfs/spa.h
index 19a2b640a..7edb8ab7d 100644
--- a/include/grub/zfs/spa.h
+++ b/include/grub/zfs/spa.h
@@ -97,7 +97,15 @@ typedef struct dva {
  * Each block has a 256-bit checksum -- strong enough for cryptographic hashes.
  */
 typedef struct zio_cksum {
+  union
+  {
 	grub_uint64_t	zc_word[4];
+	struct
+	{
+		grub_uint32_t   zc_cut_cksum[5];
+		grub_uint32_t   zc_mac[3];
+	};
+  };
 } zio_cksum_t;
 
 /*