able to create cookie but not able to update

able to create cookie but not able to update

Good evening,
i am using jquery cookie plug in that i downloaded from https://github.com/carhartl/jquery-cookie .
i am able to create cookie with this code . but not able to update cookie using jquery's on change event .  it says

TypeError: $.cookie is not a function

alert($.cookie("self"));

created cookie ,using following code :
 $.cookie('self','not_checked', { expires: 7 ,path: '/'});
it was created, i checked in browser cookies.
 i used following code for updating :
 $.cookie("self", "checked");
and also
 $.cookie('self','checked', { expires: 7 ,path: '/'});
same error  any help will be appreciated