diff --git a/ChangeLog b/ChangeLog
index 505923fa9..3e20a118b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2011-01-04  Vladimir Serbinenko  <phcoder@gmail.com>
+
+	* grub-core/lib/reed_solomon.c (grub_reed_solomon_add_redundancy):
+	Prevent overflow.
+	(grub_reed_solomon_recover): Likewise.
+
 2011-01-04  Vladimir Serbinenko  <phcoder@gmail.com>
 
 	* grub-core/lib/reed_solomon.c (main) [TEST]: Reactivate normal test.
diff --git a/grub-core/lib/reed_solomon.c b/grub-core/lib/reed_solomon.c
index 62aad3111..e500ba32d 100644
--- a/grub-core/lib/reed_solomon.c
+++ b/grub-core/lib/reed_solomon.c
@@ -433,8 +433,8 @@ grub_reed_solomon_add_redundancy (void *buffer, grub_size_t data_size,
       tt = cs + crs;
       if (tt > MAX_BLOCK_SIZE)
 	{
-	  cs = (cs * MAX_BLOCK_SIZE) / tt;
-	  crs = (crs * MAX_BLOCK_SIZE) / tt;
+	  cs = ((cs * (MAX_BLOCK_SIZE / 512)) / tt) * 512;
+	  crs = ((crs * (MAX_BLOCK_SIZE / 512)) / tt) * 512;
 	}
       encode_block (ptr, cs, rptr, crs);
       ptr += cs;
@@ -468,8 +468,8 @@ grub_reed_solomon_recover (void *ptr_, grub_size_t s, grub_size_t rs)
       tt = cs + crs;
       if (tt > MAX_BLOCK_SIZE)
 	{
-	  cs = (cs * MAX_BLOCK_SIZE) / tt;
-	  crs = (crs * MAX_BLOCK_SIZE) / tt;
+	  cs = ((cs * (MAX_BLOCK_SIZE / 512)) / tt) * 512;
+	  crs = ((crs * (MAX_BLOCK_SIZE / 512)) / tt) * 512;
 	}
       decode_block (ptr, cs, rptr, crs);
       ptr += cs;