UPDATE with SELECT not supported

Was using the php-sqllint package (says to report errors here) and got these errors on valid MySQL syntax:

Line 1, col 45 at "(": An expression was expected.
Line 1, col 45 at "(": Unexpected token.
Line 1, col 46 at "SELECT": A new statement was found, but no delimiter between it and the previous one.
Line 1, col 106 at ")": Unexpected token.
Line 1, col 108 at "src": Unexpected token.
Line 2, col 5 at "SET": A new statement was found, but no delimiter between it and the previous one.

The SQL to generate these errors is similar to this (table, column names and values are different):

UPDATE table1 t1, (SELECT `id` FROM table2 WHERE `unique_val` = 1) src
    SET t1.ref_to_t2 = src.id
    WHERE t1.unique_val = 'unique';

No se indica ningún archivo del repositorio ni ninguna prueba. Reproduce la consulta reportada mediante php-sqllint, rastrea después el análisis de UPDATE alrededor del SELECT entre paréntesis y verifica que esta sintaxis válida de MySQL se acepte sin los errores reportados.