change header title

[MartinNohr]

I can't change the header title, it always stays at the original value.
ezMenu fileMenu("Files");
ez.header.title("abc");
Serial.println("title: " + ez.header.title());
int retNum = fileMenu.runOnce();

I have also tried the ez.header.show(), same result, the header title never changes from "Files".
Any ideas on what I'm doing wrong?
Thanks.