maxlength attribute allowing more char's to type than the set value for ui:InputTextArea

Hi Guys! I'm using an InputTextArea in a component. I've set the attribute maxlength="255".

I dont know why but my ui:InputTextArea is allowing user to enter more than 255. I can see the minus count on the characters left output:

Did Any of you faced the same issue? Any Idea? why it is behaving like this.