diff --git a/ChangeLog b/ChangeLog
index 752bde8..0d42f3c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2009-07-26  Vladimir Serbinenko  <address@hidden>
+
+	* partmap/pc.c (pc_partition_map_iterate): Check that boot flags are
+	valid.
+
 2009-07-25  Felix Zielcke  <address@hidden>
 
 	* kern/file.c (grub_file_open): Revert to previous check with
diff --git a/partmap/pc.c b/partmap/pc.c
index 6f68ecf..e3ea53a 100644
--- a/partmap/pc.c
+++ b/partmap/pc.c
@@ -121,6 +121,13 @@ pc_partition_map_iterate (grub_disk_t disk,
       if (mbr.signature != grub_cpu_to_le16 (GRUB_PC_PARTITION_SIGNATURE))
 	return grub_error (GRUB_ERR_BAD_PART_TABLE, "no signature");
 
+      for (i = 0; i < 4; i++)
+	if (mbr.entries[i].flag & 0x7f)
+	  break;
+
+      if (i != 4)
+	return grub_error (GRUB_ERR_BAD_PART_TABLE, "bad boot flag");
+
       /* Analyze DOS partitions.  */
       for (p.index = 0; p.index < 4; p.index++)
 	{