diff --git a/ChangeLog b/ChangeLog
index e50863addf..56c3a624c4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Dec 15 13:50:05 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (rb_str_oct): [DOC] mention radix indicators.
+	  [ruby-core:71310] [Bug #11648]
+
 Tue Dec 15 12:20:30 2015  Takashi Kokubun  <takashikkbn@gmail.com>
 
 	* lib/erb.rb: Simplify regexp to optimize erb scanner.
diff --git a/string.c b/string.c
index 1bd7582495..2c8089b94c 100644
--- a/string.c
+++ b/string.c
@@ -8033,6 +8033,9 @@ rb_str_hex(VALUE str)
  *     "-377".oct      #=> -255
  *     "bad".oct       #=> 0
  *     "0377bad".oct   #=> 255
+ *
+ *  If +str+ starts with <code>0</code>, radix indicators are hornored.
+ *  See Kernel#Integer.
  */
 
 static VALUE