Timeline doesn't generate unique name for object when prompting to do so

If you change an object name in timeline to same name as another object under the same parent, you get a dialog warning you that the name is duplicated: "The object name is duplicated under its parent, do you want to make it unique?".

Answering yes to this dialog should append a number to the object name to make it unique, but it doesn't - it just accepts the duplicate name.