How to set response header in nestjs with fastify

I'm trying to set a custom reponse header in a nest js controller and using fastify.
Currently I'm trying to do:

@Post()
async methodName(@Res res) {
    res.set('key', 'value');
};

But I get the error:

res.set is not a function

Can someone help me?

The solution was:

res.header('key', 'value');