Eli Zaretskii <eliz@gnu.org> writes:

>> +** 'expand-file-name' now checks for null bytes in filenames.
>> +The function will now check for null bytes in both NAME and
>> +DEFAULT-DIRECTORY arguments, as well as in the 'default-directory'
>> +buffer-local variable, assuming its value is used.
>
> This should say that if null bytes are found, expand-file-name will
> signal an error.

Makes sense! I'm attaching a revised version.