diff --git a/ChangeLog b/ChangeLog
index 88941c2c12..91d1f9b3b4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Apr 25 03:08:39 2011  Tadayoshi Funaba  <tadf@dotrb.org>
+
+	* ext/date/lib/date/format.rb: require 'date'.
+
 Mon Apr 25 03:04:16 2011  Tadayoshi Funaba  <tadf@dotrb.org>
 
 	* ext/date/lib/date/format.rb (_iso8601): added a pattern.
diff --git a/ext/date/lib/date/format.rb b/ext/date/lib/date/format.rb
index cc4177a51c..6807b40d8e 100644
--- a/ext/date/lib/date/format.rb
+++ b/ext/date/lib/date/format.rb
@@ -1,5 +1,6 @@
 # format.rb: Written by Tadayoshi Funaba 1999-2011
-require 'date_core.so'
+
+require 'date'
 
 class Date