diff --git a/ChangeLog b/ChangeLog
index f6346e8f97..92f7f57cc1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Jul 11 23:54:45 2013  Masaki Matsushita  <glass.saga@gmail.com>
+
+	* hash.c (rb_hash_keys): set array capa to RHASH_SIZE().
+
 Thu Jul 11 21:30:17 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* win32/win32.c (rb_w32_pow): undef pow to get rid of infinite
diff --git a/hash.c b/hash.c
index 903cca24a0..448476a2c1 100644
--- a/hash.c
+++ b/hash.c
@@ -1651,7 +1651,7 @@ rb_hash_keys(VALUE hash)
 {
     VALUE ary;
 
-    ary = rb_ary_new();
+    ary = rb_ary_new_capa(RHASH_SIZE(hash));
     rb_hash_foreach(hash, keys_i, ary);
 
     return ary;