delete-trailing-whitespace behavior change?

[Skip Montanaro]

I've defined this hook in ~/.emacs for ages (a decade or so, I suspect):

(add-hook 'before-save-hook 'delete-trailing-whitespace)

Recently, I've noticed that the last newline of files seems to be deleted.
Not always, but pretty frequently. I'm running 25.2.2 at home and 25.3.2 at
work. I think I switched from 24 to 25 in the past few months. I can't seem
to quickly lay my hands on Emacs 24 without going through a
download/install cycle, but I wonder if delete-trailing-whitespace might
have changed between 24 and 25?

Any insight would be appreciated...

Skip Montanaro