diff --git a/ChangeLog b/ChangeLog
index d00f97e966..25350fa130 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Aug 21 05:47:00 2016  Kenta Murata  <mrkn@mrkn.jp>
+
+	* enum.c (enum_sort): prevent wasteful array duplicaion.
+
 Sat Aug 20 11:20:32 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* rubystub.c: generalize win32/stub.c.
diff --git a/enum.c b/enum.c
index f561a6845c..487ee55c7e 100644
--- a/enum.c
+++ b/enum.c
@@ -938,7 +938,7 @@ enum_first(int argc, VALUE *argv, VALUE obj)
 static VALUE
 enum_sort(VALUE obj)
 {
-    return rb_ary_sort(enum_to_a(0, 0, obj));
+    return rb_ary_sort_bang(enum_to_a(0, 0, obj));
 }
 
 #define SORT_BY_BUFSIZE 16