False unread messages in Messages

Messages are synced with iCloud between my MacBook and iPhone. When an unread message is deleted (happens when using auto-fill on a webpage for a security code text message, Messages automatically deletes the unread message after the auto-fill), the Messages icon still shows an unread message notification. There are no unread messages, it's a false notification that cannot be cleared. Annoying, because it looks like I really do have an unread message. And it's APPLE that deleted the message when doing the auto-fill, so the system should KNOW that the unread message has been deleted. and should get fixed. In the meantime, how can I clear the "ghost" unread message notification? I've tried quitting Messages and restarting, but it's still reporting an unread message which doesn't exist.

[Edited by Moderator]