mysqljs ER_PARSE_ERROR in valid request - mysql

Question

I'm using mysqljs and I want to delete a row in a table with its id:
class_id is the id (string).
connection.query(
`DELETE FROM classes WHERE id = ?`, [class_id], (err, result) => {
if (err) throw(err);
resolve();
}
);
Connection:
global.connection = mysql.createPool({
connectionLimit : 10,
host : config.mysql.hostname,
user : config.mysql.user,
password : config.mysql.password,
database : config.mysql.database,
charset: 'utf8'
});
But I got this error:
Error: ER_PARSE_ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DELETE FROM classes WHERE id = 'C2'' at line 1
at Query.Sequence._packetToError (C:\Users\admin\Documents\main\node_modules\mysql\lib\protocol\sequences\Sequence.js:47:14)
at Query.ErrorPacket (C:\Users\admin\Documents\main\node_modules\mysql\lib\protocol\sequences\Query.js:77:18)
at Protocol._parsePacket (C:\Users\admin\Documents\main\node_modules\mysql\lib\protocol\Protocol.js:278:23)
at Parser.write (C:\Users\admin\Documents\main\node_modules\mysql\lib\protocol\Parser.js:76:12)
at Protocol.write (C:\Users\admin\Documents\main\node_modules\mysql\lib\protocol\Protocol.js:38:16)
at Socket.<anonymous> (C:\Users\admin\Documents\main\node_modules\mysql\lib\Connection.js:91:28)
at Socket.<anonymous> (C:\Users\admin\Documents\main\node_modules\mysql\lib\Connection.js:502:10)
at emitOne (events.js:116:13)
at Socket.emit (events.js:211:7)
at addChunk (_stream_readable.js:263:12)
--------------------
I tried to execute the request manually and it works great.
Can someone help me?