Query with nested include and custom join condition

I am using master.
I prepared gist with 3 files: .js is actual test, .json is json output from test and .sql is SQL generated by Sequelize that makes sequelize to produce invalid result.
https://gist.github.com/alekbarszczewski/e66cbb99f95debf1e4ce

Basically what I want is:

Playlist.find({
            where: { id: 1 },
            include: [
                {
                    model: Post,
                    where: [
                        'EXISTS('+
                        'SELECT "PostTranslations2"."id" '+
                        'FROM "PostTranslations" AS "PostTranslations2"'+
                        'WHERE "PostTranslations2"."lang" = \'en-us\' AND "Posts"."id" = "PostTranslations2"."PostId"'+
                        ')'
                    ],
                    required: false,
                    include: [
                        { model: PostTranslation, where: { lang: 'en-us' }, required: false }
                    ]
                }
            ]   
        })

Unfortunately it does not work (you can see in gist) because my custom join query (EXISTS(...)) is applied to wrong JOIN table. Joins are as follows:

Playlists -> PlaylistsPosts -> *Posts* -> PostTranslations

Is it possible to apply custom join condition to PlaylistsPosts in this query?
Maybe there is other workaround?

I guess I could do something like:

Playlist.find({
   include: [{ model: PlaylistsPosts, include: [{ model: Post }] }]
})

But then I would get result in wrong format -> each playlist would have playlistsPosts and then each playlistsPost would have post attribute...

Start with the three gist files: the .js reproduction, the .json output, and the .sql generated query; compare the nested include and its joins, especially PlaylistsPosts, Posts, and PostTranslations. Done means the custom EXISTS condition is applied to the intended join while preserving the requested playlist-to-post result shape.