sequelize: update method tries to insert null when receiving undefined

What you are doing?

I map some request to Sequelize model :

        var model = {
            title: req.body.title,
            description: req.body.description
        };
        models.job.update(model, {..}).then(() => {})

let say that req.body.title is undefined and req.body.description has value. In the model, title cant be null. For some reason sequelize tries to insert null to the title although it is undefined, resulting in getting the following error :

err.stack SequelizeValidationError: notNull Violation: title cannot be null

this happens probably because model.hasOwnProperty(‘title’) returns true, but yet, model.title is undefined and not null

What do you expect to happen?

I think that in that case, when a field is undefined, Sequelize should not try to insert null into it (the title field) and just ignore it

What is actually happening?

i get an error :

err.stack SequelizeValidationError: notNull Violation: title cannot be null

I think we should insert null only when someone specifically specify that this field is null.

Dialect: mysql __Database version: 5.7.9 __Sequelize version: 3.28.0