Apostrophe in username

[Dom Latter]

We are using a mysql-backed v3 server and eap / peap / mschapv2.

A new user has come along whose email address contains an apostrophe,
('single quote' if you prefer) which is unusual but legitimate.

By default we allow users to use their email address as a username.

I have found the safe_characters list here:
/etc/freeradius/mods-config/sql/main/mysql/queries.conf

Without the apostrophe in the safe_characters list, it gets encoded to
=27 and so the db query [1] fails to find a user with that username.

With the apostrophe in the list, the query fails with "an error in your
SQL syntax"...

Is there any way out of this conundrum except putting mime-encoded
data in the database?

[1] authorize_check_query from sql/mysql/dialup.conf