diff --git a/ChangeLog b/ChangeLog
index 622fc3c3bf..065dc035ef 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Jun 28 12:26:53 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (rb_big_and): Allocate new bignum with same size to shorter
+	  argument if it's high bits are zero.
+
 Fri Jun 28 12:14:04 2013  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/ipsocket.c (init_inetsock_internal): Don't use local
diff --git a/bignum.c b/bignum.c
index 6087d3a13b..2ec83b8077 100644
--- a/bignum.c
+++ b/bignum.c
@@ -4747,6 +4747,9 @@ rb_big_and(VALUE x, VALUE y)
     hibits1 = hibitsx;
     hibits2 = hibitsy;
 
+    if (!hibits1)
+        l2 = l1;
+
     z = bignew(l2, 0);
     zds = BDIGITS(z);