diff --git a/ChangeLog b/ChangeLog
index 2ab9a1e98d..029b65c768 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Dec 22 14:45:21 2007  Tadayoshi Funaba  <tadf@dotrb.org>
+
+	* lib/date.rb: shouldn't freeze nil. [ruby-dev:32677]
+
 Sat Dec 22 14:27:27 2007  Tanaka Akira  <akr@fsij.org>
 
 	* regenc.c (onigenc_ascii_is_code_ctype): moved from enc/ascii.c.
diff --git a/lib/date.rb b/lib/date.rb
index 5629730941..d2359bf3ba 100644
--- a/lib/date.rb
+++ b/lib/date.rb
@@ -6,7 +6,7 @@
 # Documentation: William Webber <william@williamwebber.com>
 #
 #--
-# $Id: date.rb,v 2.32 2007-12-01 18:51:16+09 tadf Exp $
+# $Id: date.rb,v 2.33 2007-12-22 14:41:34+09 tadf Exp $
 #++
 #
 # == Overview
@@ -250,7 +250,7 @@ class Date
   ABBR_DAYNAMES = %w(Sun Mon Tue Wed Thu Fri Sat)
 
   [MONTHNAMES, DAYNAMES, ABBR_MONTHNAMES, ABBR_DAYNAMES].each do |xs|
-    xs.each{|x| x.freeze}.freeze
+    xs.each{|x| x.freeze unless x.nil?}.freeze
   end
 
   class Infinity < Numeric # :nodoc: