InvalidBasesError: Cannot resolve bases for []

When I run tests I get this error during database initialization:

django.db.migrations.state.InvalidBasesError: Cannot resolve bases for [<ModelState: 'users.GroupProxy'>]This can happen if you are inheriting models from an app with migrations (e.g. contrib.auth)

I created this proxy for contrib.auth Group model to place it in my app in django admin:

class GroupProxy(Group):    class Meta:        proxy = True        verbose_name = Group._meta.verbose_name        verbose_name_plural = Group._meta.verbose_name_plural

So what can I do to fix this issue?