Has lexical binding declaration format changed in Emacs 30 or 31?

Hi all,

I started seeing the byte compiler generating the

"Warning (bytecomp): file has no ‘lexical-binding’ directive on its first
line"

for files that do have the declaration.

For example, the file:
gnu-elpa-keyring-update-2025.10.1/gnu-elpa-keyring-update.el

The first line of the file seems OK to me:

;;; gnu-elpa-keyring-update.el --- Update Emacs's GPG keyring for GNU ELPA
 -*- lexical-binding: t; -*-

I have seen this on
GNU Emacs 30.2.50 (build 2, aarch64-apple-darwin23.6.0, NS appkit-2487.70
Version 14.8.2 (Build 23J126)) of 2025-11-26

Has the format requirement changed for Emacs 30 or 31?

-- 
/Pierre