how to change a property in an itemupdated event receiver?

Hi, I have a very simple code but it doesn't change the property

public  override  void  ItemUpdated(SPItemEventProperties  properties){
            base .ItemUpdated(properties);using(DisabledEventsScope  scope =new  DisabledEventsScope ()){
                SPListItem  listItem = properties.ListItem;
                listItem["Title"]="A cool new title!";
                listItem.Update();}}

it doesn't throw errors but the property is not being changed.

Note: I'm working with form library.

luis molina