diff --git a/ChangeLog b/ChangeLog
index f7625c1dc8..dd8b75809d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Jun 27 11:06:05 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/un.rb (wait_writable): added help message.
+
 Fri Jun 27 06:52:54 2008  Koichi Sasada  <ko1@atdot.net>
 
 	* configure.in: need a ",".
diff --git a/lib/un.rb b/lib/un.rb
index 4512c83181..ee40d36d62 100644
--- a/lib/un.rb
+++ b/lib/un.rb
@@ -19,6 +19,7 @@
 #   ruby -run -e install -- [OPTION] SOURCE DEST
 #   ruby -run -e chmod -- [OPTION] OCTAL-MODE FILE
 #   ruby -run -e touch -- [OPTION] FILE
+#   ruby -run -e wait_writable -- [OPTION] FILE
 #   ruby -run -e help [COMMAND]
 
 require "fileutils"
@@ -218,6 +219,10 @@ end
 #
 #   ruby -run -e wait_writable -- [OPTION] FILE
 #
+#   -n RETRY	count to retry
+#   -w SEC	each wait time in seconds
+#   -v		verbose
+#
 
 def wait_writable
   setup("n:w:v") do |argv, options|