diff --git a/ChangeLog b/ChangeLog
index c921a22371..c10f29d97f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Jul  9 22:17:58 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (bary_mul1): No need to invoke MEMZERO at last.
+
 Tue Jul  9 21:40:01 2013  Kouhei Sutou  <kou@cozmixng.org>
 
 	* test/rexml/test_text.rb: Add missing tests for Text#<<.
diff --git a/bignum.c b/bignum.c
index b742bb4ac5..b64e477b29 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1800,7 +1800,6 @@ bary_mul1(BDIGIT *zds, size_t zl, BDIGIT *xds, size_t xl, BDIGIT *yds, size_t yl
         bary_mul_normal(zds, zl, xds, xl, yds, yl);
         rb_thread_check_ints();
     }
-    MEMZERO(zds + l, BDIGIT, zl - l);
 }
 
 /* determine whether a bignum is sparse or not by random sampling */