Config.collectionName doesn't seem to work

[vparpoil]

First thanks for your package, I have been using it for a while and works perfectly !
I wanted to configure a config with a custom collection name but it doesn't seem to work. I have two apps on the same database, and would like to handle 2 separate flows of migrations.
Code snippet imports/startup/server/index.js:

Meteor.startup(function () { 
    Migrations.config({
        collectionName: "migrationssecondapp"
    });
    Migrations.unlock();
    Migrations.migrateTo(1);
}

error : Error: [Can't find migration version 7], at Object.Migrations._findIndexByVersion
Version 7 is the version I migrated in the other app.

Trying to log Migrations._collection still gives the collection migrations.

METEOR@1.6.0.1
percolate:migrations@1.0.2

Any hint on how to fix ? I could do a PR if needed
Thanks a lot