Is it possible to begin migrating users in to an Auth0 database connection that already contains users?

We have an Auth0 database connection that contains some users. I’d like to now begin migrating users from our legacy database into this Auth0 database, but switching on the “Use my own database” option in Connections>Database>Custom Database give me the message:

This database contains 40 users. You cannot change “options.enabledDatabaseCustomization” setting.

It seems fairly clear but I thought that I’d ask just in case. Googling hasn’t helped.

To my knowledge the warning you received is unavoidable and you’ll have to initiate the move to a custom database with migration in a connection with no users.