diff --git a/ChangeLog b/ChangeLog
index fb54b94992..ee8e605fad 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Sep 10 12:05:04 2013  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
+
+	* io.c (rb_f_printf): [DOC] add missing parenthesis in rdoc.
+
 Tue Sep 10 10:08:00 2013  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
 
 	* NEWS: Update RubyGems note.
diff --git a/io.c b/io.c
index 8d2ed8d06c..ec0715fcea 100644
--- a/io.c
+++ b/io.c
@@ -6732,9 +6732,9 @@ rb_io_printf(int argc, VALUE *argv, VALUE out)
  *     printf(string [, obj ... ])        -> nil
  *
  *  Equivalent to:
- *     io.write(sprintf(string, obj, ...)
+ *     io.write(sprintf(string, obj, ...))
  *  or
- *     $stdout.write(sprintf(string, obj, ...)
+ *     $stdout.write(sprintf(string, obj, ...))
  */
 
 static VALUE