Quay 3.4 SMTP validation fails

Upgrade from Quay 3.3 to 3.4, validation on startup fails with the following error message:

• You must enable tls if you wish to use plain auth credentials. Error: 504 5.7.4 Unrecognized authentication type

However, SMTP settings seem to be correct and this setup was working on Quay 3.3:

MAIL_DEFAULT_SENDER: quay-noreply@DOMAIN
MAIL_PASSWORD: <%= @mail_passwd %>
MAIL_PORT: 587
MAIL_SERVER: MAIL_SERVER_HERE
MAIL_USERNAME: username
MAIL_USE_AUTH: true
MAIL_USE_TLS: true

Please check, thank you!