diff --git a/ChangeLog b/ChangeLog
index a52ad91f82..b4d3d1ef60 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Sep  2 14:39:29 2013  Akinori MUSHA  <knu@iDaemons.org>
+
+	* ruby.c (Process#setproctitle): Fix and improve rdoc.
+
+	* ruby.c (Process#argv0): Improve rdoc.
+
 Mon Sep  2 14:15:00 2013  Kenta Murata  <mrkn@cookpad.com>
 
 	* NEWS: fix description of number literal suffixes.
diff --git a/ruby.c b/ruby.c
index 9e5a5168d4..6723d200cf 100644
--- a/ruby.c
+++ b/ruby.c
@@ -1787,6 +1787,9 @@ rb_load_file_str(VALUE fname_v)
  *
  *  Returns the name of the script being executed.  The value is not
  *  affected by assigning a new value to $0.
+ *
+ *  This method first appeared in Ruby 2.1 to serve as a global
+ *  variable free means to get the script name.
  */
 
 static VALUE
@@ -1799,12 +1802,17 @@ proc_argv0(VALUE process)
  *  call-seq:
  *     Process.setproctitle(string)  -> string
  *
- *  Returns the process title that appears on the ps(1) command.  Not
- *  necessarily effective on all platforms.
+ *  Sets the process title that appears on the ps(1) command.  Not
+ *  necessarily effective on all platforms.  No exception will be
+ *  raised regardless of the result, nor will NotImplementedError be
+ *  raised even if the platform does not support the feature.
  *
  *  Calling this method does not affect the value of $0.
  *
  *     Process.setproctitle('myapp: worker #%d' % worker_id)
+ *
+ *  This method first appeared in Ruby 2.1 to serve as a global
+ *  variable free means to change the process title.
  */
 
 static VALUE