diff --git a/ChangeLog b/ChangeLog
index 6293fa5395..577b810064 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Dec 10 09:32:51 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/mkmf.rb, lib/shellwords.rb: disable frozen-string-literal.
+	  [ruby-core:72011] [Bug #11800]
+
 Thu Dec 10 06:33:39 2015  Eric Wong  <e@80x24.org>
 
 	* marshal.c (memsize_dump_arg): remove NULL check
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index d515382c17..d8bc1b525d 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -1,4 +1,5 @@
 # -*- coding: us-ascii -*-
+# frozen-string-literal: false
 # module to create Makefile for extension modules
 # invoke like: ruby -r mkmf extconf.rb
 
diff --git a/lib/shellwords.rb b/lib/shellwords.rb
index 2b72750a6b..ccc1c31060 100644
--- a/lib/shellwords.rb
+++ b/lib/shellwords.rb
@@ -1,3 +1,4 @@
+# frozen-string-literal: false
 ##
 # == Manipulates strings like the UNIX Bourne shell
 #