Short URL not generated when using alias.

[giladrom]

I am unable to generate short URLs using aliases.

The generateShortUrl() function works fine without an alias:

 var analytics = {
              channel: 'app',
              feature: 'invite',
              stage: 'new user',
     };

var link_properties = {
              $desktop_url: 'https://app.com/',
              $android_url:
                'https://play.google.com/store/apps/details?id=XXX',
              $ios_url: 'itms-apps://itunes.apple.com/app/XXX',
              $ipad_url: 'itms-apps://itunes.apple.com/app/XXX',
    };

branch_universal_obj.generateShortUrl(analytics, link_properties).then(res => ...)

Gives me the proper URL:

https://subdomain.app.com/vEGJFJcsDS

However, when adding the alias variable to the analytics object, I get the long URL:

var analytics = {
              channel: 'app',
              feature: 'invite',
              stage: 'new user',
              alias: 'ALIAS12'
     };

...

branch_universal_obj.generateShortUrl(analytics, link_properties).then(res => ...)

Gives me:

 {"url":"https://app.sample.com/a/key_live_XXXXXXX?%24identity_id=123456678&alias=ALIAS12&channel=app&feature=invite&stage=new%20user&source=ios&data=....."}