Combine multiple auths with passport, express & NodeJS

I'm trying to combine a LinkedInStrategy with an existing LocalStrategy (user is already authenticated).

Here is the example from passport docs :

schema.statics.passportLinkedInStrategy = function(token, tokenSecret, profile, done) {
    // asynchronous verification, for effect...
    process.nextTick(function () {
        // To keep the example simple, the user's LinkedIn profile is returned to
        // represent the logged-in user.  In a typical application, you would want
        // to associate the LinkedIn account with a user record in your database,
        // and return that user instead.
        return done(null, profile);
    });
};

Problem is I don't have access to req.user to check the existing session in this callback.

Any idea on how I could/should do it?