diff --git a/ChangeLog b/ChangeLog
index 81e4774d5c..811ba85d77 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Nov 16 16:39:38 2015  Akinori MUSHA  <knu@iDaemons.org>
+
+	* lib/set.rb: Enable frozen_string_literal.
+
+	* lib/set.rb: Move << out of the begin block that ensures pop.
+
 Mon Nov 16 16:28:30 2015  Akinori MUSHA  <knu@iDaemons.org>
 
 	* lib/set.rb (Hash#flatten!, #add?, #delete?, #collect!, #reject!,
diff --git a/lib/set.rb b/lib/set.rb
index a0f290ebed..a8f4345f35 100644
--- a/lib/set.rb
+++ b/lib/set.rb
@@ -1,4 +1,6 @@
 #--
+# frozen_string_literal: true
+#
 # set.rb - defines the Set class
 #++
 # Copyright (c) 2002-2013 Akinori MUSHA <knu@iDaemons.org>
@@ -534,8 +536,8 @@ class Set
       return sprintf('#<%s: {...}>', self.class.name)
     end
 
+    ids << object_id
     begin
-      ids << object_id
       return sprintf('#<%s: {%s}>', self.class, to_a.inspect[1..-2])
     ensure
       ids.pop