diff --git a/ChangeLog b/ChangeLog
index df26877d3d..49c286b71c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,7 @@
 Thu May 13 12:53:13 2010  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* io.c (swallow): support text mode and UTF-16/32 as internal encoding.
+	  [Bug #1576]
 
 	* io.c (io_shift_cbuf): read and throw it away when str is NULL.