diff --git a/ChangeLog b/ChangeLog
index 8661726df..bdd5697ab 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2015-01-20  Vladimir Serbinenko  <phcoder@gmail.com>
+
+	* grub-core/disk/ieee1275/nand.c (grub_nand_open): Check block size
+	validity.
+
 2015-01-20  Vladimir Serbinenko  <phcoder@gmail.com>
 
 	* grub-core/disk/dmraid_nvidia.c (grub_dmraid_nv_detect): Do not
diff --git a/grub-core/disk/ieee1275/nand.c b/grub-core/disk/ieee1275/nand.c
index 576e9ccc4..feffa8c4c 100644
--- a/grub-core/disk/ieee1275/nand.c
+++ b/grub-core/disk/ieee1275/nand.c
@@ -113,6 +113,11 @@ grub_nand_open (const char *name, grub_disk_t disk)
     }
 
   data->block_size = (args.size1 >> GRUB_DISK_SECTOR_BITS);
+  if (!data->block_size)
+    {
+      grub_error (GRUB_ERR_UNKNOWN_DEVICE, "invalid block size");
+      goto fail;
+    }
 
   INIT_IEEE1275_COMMON (&args.common, "call-method", 2, 3);
   args.method = (grub_ieee1275_cell_t) "size";