diff --git a/ChangeLog b/ChangeLog
index 0f702895c3..b686759bdd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Jan 12 02:14:43 2012  Ayumu AIZAWA  <ayumu.aizawa@gmail.com>
+
+	* object.c: Added examples for Object#is_a? and
+	  Object#instance_of? patcheed from Manoj Kumar.
+	  [Bug #5880] [ruby-core:42057]
+
 Thu Jan 12 00:57:48 2012  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
 
 	* lib/mkmf.rb: verbose-mode can use by RM, RMDIRS, etc.
diff --git a/object.c b/object.c
index 24d85d428b..09b3999231 100644
--- a/object.c
+++ b/object.c
@@ -490,6 +490,15 @@ rb_obj_inspect(VALUE obj)
  *
  *  Returns <code>true</code> if <i>obj</i> is an instance of the given
  *  class. See also <code>Object#kind_of?</code>.
+ *
+ *     class A;     end
+ *     class B < A; end
+ *     class C < B; end
+ *
+ *     b = B.new
+ *     b.instance_of? A   #=> false
+ *     b.instance_of? B   #=> true
+ *     b.instance_of? C   #=> false
  */
 
 VALUE
@@ -524,11 +533,13 @@ rb_obj_is_instance_of(VALUE obj, VALUE c)
  *     end
  *     class B < A; end
  *     class C < B; end
+ *
  *     b = B.new
- *     b.instance_of? A   #=> false
- *     b.instance_of? B   #=> true
- *     b.instance_of? C   #=> false
- *     b.instance_of? M   #=> false
+ *     b.is_a? A          #=> true
+ *     b.is_a? B          #=> true
+ *     b.is_a? C          #=> false
+ *     b.is_a? M          #=> true
+ *
  *     b.kind_of? A       #=> true
  *     b.kind_of? B       #=> true
  *     b.kind_of? C       #=> false