Heroku Postgres: Unhandled rejection Error: self signed certificate - node.js

Question

I'm trying to configure the PostgreSQL database with postgrator in node, using the connectionString in production. I've added the code for initialization in node
const postgrator = new Postgrator(migrationConfig);
postgrator.migrate('002', (err, migrations) => {
if (err) {
console.error(err);
} else {
console.log(migrations);
}
postgrator.endConnection();
});
const isDevelopment = process.env.NODE_ENV === 'development';
let migrationConfig;
if (isDevelopment) {
migrationConfig = {
"migrationDirectory": "migrations",
"driver": "pg",
"host": process.env.DEV_DB_HOST,
"port": process.env.DEV_DB_PORT,
"database": process.env.DEV_DB_DATABASE,
"username": process.env.DEV_DB_USER,
"password": process.env.DEV_DB_PASS,
"ssl": !isDevelopment,
}
} else {
migrationConfig = {
"migrationDirectory": "migrations",
"driver": "pg",
"connectionString": process.env.DATABASE_URL,
"ssl": true,
}
}
I'm not sure why I'm getting the self signed certificate error on production.
2020-10-18T10:04:49.845485+00:00 app[web.1]: > export NODE_ENV=production && nodemon src/server.js
2020-10-18T10:04:49.845485+00:00 app[web.1]:
2020-10-18T10:04:50.082326+00:00 app[web.1]: [nodemon] 2.0.4
2020-10-18T10:04:50.083611+00:00 app[web.1]: [nodemon] to restart at any time, enter `rs`
2020-10-18T10:04:50.084275+00:00 app[web.1]: [nodemon] watching path(s): *.*
2020-10-18T10:04:50.084383+00:00 app[web.1]: [nodemon] watching extensions: js,mjs,json
2020-10-18T10:04:50.085033+00:00 app[web.1]: [nodemon] starting `node src/server.js`
2020-10-18T10:04:50.489740+00:00 app[web.1]: Express is listening on port 48474
2020-10-18T10:04:50.535273+00:00 app[web.1]: Unhandled rejection Error: self signed certificate
2020-10-18T10:04:50.535275+00:00 app[web.1]: at TLSSocket.onConnectSecure (_tls_wrap.js:1502:34)
2020-10-18T10:04:50.535276+00:00 app[web.1]: at TLSSocket.emit (events.js:314:20)
2020-10-18T10:04:50.535276+00:00 app[web.1]: at TLSSocket._finishInit (_tls_wrap.js:937:8)
2020-10-18T10:04:50.535277+00:00 app[web.1]: at TLSWrap.ssl.onhandshakedone (_tls_wrap.js:711:12)
2020-10-18T10:04:51.077573+00:00 heroku[web.1]: State changed from starting to up
I've upgraded the dyno to a paid service to activate the SSL, yet this error still continues to come up. I saw online suggestin to set rejectUnauthorized to false`, but postgrator does not provide that option. Even if I set it to the Postgres configuration the issue seems to still persist.
How do I fix this?