diff --git a/ChangeLog b/ChangeLog
index 653bdf8cb7..afe31ff233 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Oct 14 18:27:18 2016  SHIBATA Hiroshi  <hsbt@ruby-lang.org>
+
+	* object.c: Improve documentation for Integer conversion.
+	  [ruby-core:71661][Bug #11736][ci skip]
+
 Fri Oct 14 18:00:20 2016  SHIBATA Hiroshi  <hsbt@ruby-lang.org>
 
 	* lib/logger.rb: Improve Logger.new option documentation.
diff --git a/object.c b/object.c
index 451746150d..9769c1ee26 100644
--- a/object.c
+++ b/object.c
@@ -2968,11 +2968,14 @@ FUNC_MINIMIZED(static VALUE rb_f_float(VALUE obj, VALUE arg));
  *     Float(arg)    -> float
  *
  *  Returns <i>arg</i> converted to a float. Numeric types are converted
- *  directly, the rest are converted using <i>arg</i>.to_f.
+ *  directly, and with exception to string and nil the rest are converted using <i>arg</i>.to_f.
+ *  Converting a <code>string</code> with invalid characters will result in a <code>ArgumentError</code>.
  *  Converting <code>nil</code> generates a <code>TypeError</code>.
  *
- *     Float(1)           #=> 1.0
- *     Float("123.456")   #=> 123.456
+ *     Float(1)                 #=> 1.0
+ *     Float("123.456")         #=> 123.456
+ *     Float("123.0_badstring") #=> ArgumentError: invalid value for Float(): "123.0_badstring"
+ *     Float(nil)               #=> TypeError: can't convert nil into Float
  */
 
 static VALUE