Knex / Objection / PostgreSQL - Update of foreign key not working - postgresql

Question

I use Knex/Objection with PostgreSQL and I'm trying to update the foreign key but it returns null without any error.
Car model:
export class CarModel extends Model implements Car {
public static readonly tableName: string = 'cars';
public static readonly idColumn: string = 'car_id';
public static readonly jsonSchema: object = {
type: 'object',
properties: {
name: { type: 'string' },
carBrandId: { type: ['number', 'null'] },
lastUpdated: { type: ['string', 'null'], format: 'date-time' }
}
};
public static readonly relationMappings: RelationMappings = {
carBrandId: {
relation: Model.BelongsToOneRelation,
modelClass: 'brand.model',
join: {
from: 'brands.brand_id',
to: 'cars.fk_cars_brands'
}
}
};
public carId: number;
public name: string;
public carBrandId: number;
}
Creation of cars table:
import { Knex } from 'knex';
export function up(knex: Knex): Promise<boolean | void> {
return knex.schema.hasTable('cars').then(function(exists) {
if (!exists) {
return knex.schema.createTable('cars', (table) => {
table.specificType('car_id', 'INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY');
table.specificType('name', 'TEXT').notNullable();
table.specificType('car_brand_id', 'INTEGER').references('brand_id').inTable('brands').withKeyName('fk_cars_brands');
table.specificType('last_updated', 'TIMESTAMP');
});
}
})
}
export function down(knex: Knex): Knex.SchemaBuilder {
return knex.schema.dropTableIfExists('cars');
}
And then I use patch method in my service to update car_brand_id value from default to new added brand:
Database.getConnection().then((connection) => {
return CarModel.query(connection)
.patch({
carBrandId: 1, // row with brandId=1 exists in table brands!
lastUpdated: new Date().toISOString()
})
.where('carId', 10)
.returning('*')
.first()
});
And it returns the row where lastUpdated was updated, but carBrandId is still null:
{ carId: 10, name: 'Ferrari', carBrandId: null, lastUpdated: '<some date>' }
I would appreciate any help!